You know I love this, since I mentioned a similar version elsewhere already as an alternative to "gain XP when you reach +/-4 with someone and reset to +/-1".

Allow me a quick rewrite for clarity:

When a bond is broken, abandoned, complete, or rendered moot, ask the player with whom you had the bond (the target player) to choose one for you and one for them. They can choose either item for each player.
- Remove the bond, adjust your total bond score with the target character, and take 2 XP.
- Write a new bond with the other character, at either +1 or -1, at the target player's choice.

Did I get that right? The typical options would be:

My character was slighted: I take 2 XP or give myself a +1 bond with you, and give you a -1 bond with me.
My character was happy with how things turned out: I take 2 XP or give myself a new +1 bond with you, and give you 2 XP or give you a new +1 bond with me.

The only issue is that making a move is a player's decision, and if you've slighted another character, you may not wish to make the move. However, one might argue that by doing the thing fictionally, any player (other player and GM included) may posit that you in fact made the move.

I like this move because it makes the fiction of the bond tangible and lends more impact to the internal party relationships.

Fixed in the Adventurer's Guild release. Should read: serpents that swallow magic.

On the Giant Fighter, not saying you're wrong, but interested in knowing why, instead of re-introducing the "lost" Go Aggro move from AW as the Giant Fighter's ability, why not say:

Giant Fighter
You can use +Str instead of +Cha when you Parley, and you're always considered to  have leverage on a smaller opponent.

Extending the quote somewhat, it reads

Defy Danger is for those times when it seems like you clearly should be rolling, but no other move applies. Defy Danger also applies when you make another move despite danger not covered by that move.

I've been reading this as "when the inherent danger in what you're trying to accomplish isn't built into a more obvious move, you're going to need to DD first to get a chance to accomplish that move". As in:

GM: "Hey Nekhbet, the scorpion-men are stabbing you with their vicious hooked swords and poison stingers. Their leader is asking you questions about where you hid the treasure."
Nekhbet: "Okay I'm gonna Defy Danger and cast Jigsaw Organ Condition on the leader so his lungs fall out and he dies of suffocation."
GM: "Okay, first you have to Defy Danger, the danger being their stingers. Roll it."
Nekhbet: [rolls, gets a 7-9] "Shit, that complicates things, no?"
GM: "Right, so, you ramble off the first couple of syllables, but then spot a stinger racing towards your face. You crouch down, it misses you, you quickly scurry out of the way of the next one, but your concentration is lost. Their leader starts waving this wand made out of a human skull-and-spine towards your general direction and mumbling in some guttural language you don't recognize. What do you do now?"

In other words, the GM recognizes that Nekhbet shouldn't be hurt or receive any other imminent major consequences of failure, because he did succeed at defying the immediate danger. However, the GM is now putting Nekhbet in a spot - he is once again under threat by the stingers, and now additionally threatened by this unknown curse their leader is concocting. If he proceeds with casting his spell now, he will get pierced by those stingers; if he evades the danger of the stingers, he will get afflicted by the curse. Hopefully he has a friend nearby who can help with at least one of those (such as Defending him from the stingers), else he's pretty much fucked.

On a 10+, Nekhbet would've ducked around the stingers, completing the verbal and somatic components of the spell and getting a chance to roll to properly Cast it (with yet more risk of failure or half-hits, as Ludanto points out).
On a 6-, perhaps Nekhbet would've gotten hurt by the stingers (the obvious choice), or become overrun and pinned, or the spell backfired due to the distraction.

That's how I'm reading it, at least. I'm not sure how else you would run this situation - just tell Nekhbet that if he attempts anything but Defy Danger, Hack & Slash, or Defend, he's just going to fail in the end due to the imminent melee danger he's in?

If it's the case that Defend works the way mease19 describes, then the move should probably be rewritten slightly.

Defend (Con)
When you stand in defense of yourself, another person, item, or location under attack, roll +Con. On a 10+, Hold 3. On a 7-9, Hold 1. So long as you stand in defense, when you or the thing you defend is attacked you may spend hold, 1 for 1, to choose an option:
• If defending something other than yourself, redirect an attack from the thing you defend to yourself
• Halve the attack’s effect or damage
• Open up the attacker to an ally giving that ally +1 forward against the attacker
• Deal damage to the attacker equal to your level

In addition, to Kevin, remember the mantra of always tying it back into fiction (which I'm slowly grasping myself).

GM: "The lizardman snarls and says "Mmmm tasty elf!" and tries to stab you with a spear, what do you do?"
Player: "I hold up my bag of books to defend myself"
GM: [asking "how do you do that"] "Really? With a bag of books? Not a shield or something more suitable?"
Player: "Listen, my book bag is filled to the brim with old tomes. It's a perfect tool to block a piercing weapon like a spear."
GM: "Cool, roll it."
[Player rolls, gets a 10+]
Player: "So, I halve the attack’s effect or damage, open up the attacker to an ally, and deal 2 - my level - of damage to the attacker."
GM: "Okay, great! So, the lizardman snarls and stabs into your book bag, hard. You take 2 points of damage as you stagger backwards from the impact, hitting your head on a stalagmite. But he's unbalanced, giving Brianne here an momentary opening to slash him in the back is she chooses to. You do some damage too, how do you do that?"
Player: "Oh, I, um, see a sharp rock and hurls it at his head."
GM: "Okay, you give him a big gash in the forehead with the sharp rock. Also, there's now a deep cut in the fabric of your book bag. What's the heaviest tome you have in there?"
Player: "Oh, probably the 'Compleat Treatise on the Kingdom of Insectoides' by Lavellus Tor."
GM: "Yeah, you're pretty sure that's what the spear's tip got stopped by. Gee, I hope it didn't ruin the chapter on the mating habits of firebeetles, that was an exceptional work of science, and the only one that exists as far as you know."
Player: "Oh crap."

This perceived increase is also offset the "standard" way, which is by reduced damage output and hitpoints gained.

Cleric: Damage d6, base HP 6
Wizard: Damage d4, base HP 4
Fighter: Damage d10, base HP 7
Thief: Damage d8, base HP 5

It all seems to work nicely with the "old school" feel of Wizards, and to some degree Clerics, being relatively weaker at level 1, but a level 10 Wizard or Cleric is very powerful by comparison to non-casting classes. Contrast with DnD 4E where the power progression between casting and fighting classes is more stable.

However, I really like the notion Sage presents where non-casting classes gain access to more special options, while casters basically gain more options with regards to their casting. Really, what it's about is not becoming more powerful as you level up, but gaining more options - this makes you more adaptable, and leads to continuously fresh gameplay.

I ran the game last Friday for the first time. It was a fun time, I got some useful feedback on how I ran it, and I expect subsequent runs will be even better.

One issue we ran into was that I was unintentionally working with multiple versions. I had the full "Adventurer's Guild" version, and had just gotten the "Red Book" version as well. I figured "Red Book" was the more up-to-date as it was going to be released to the public, so used this for the Basic & Special Moves, and printed off the four playbooks for Fighter, Thief, Wizard, and Cleric classes. I also had the Ranger, Paladin, and Bard printed off from the full AG version, in case someone picked those. These latter three had no playbooks.

Turned out we got a Fighter, a Thief, a Cleric, and a Ranger. Since I had no playbook for the Ranger, I printed the one from the DW Hack. However, as we went through character creation, it became clear that the version of the Ranger in DW Hack was slightly different from the version in full AG. During play we also encountered another few niggling issues, I think, like starting equipment bundles vs starting gold, etc. Not sure if we used some incorrect versions of Moves or not.

So, given that one has access to all three versions:

• DW Hack
• DW full AG
• DW Red Book

Which should be used, which should be ignored, and which are compatible?

Also, will playbooks for the 7 classes in DW full AG version become available sometime? Or are they around somewhere and I'm just missing them?

This is an issue that runs throughout DW and AW both, and is compensated for through the fact that the game is a "conversation" and not a math game.

What I've found is that in play, and with some experience with the game, players automatically adjusts what they believe to be acceptable fictional actions / mechanical moves based on prior outcome and narration. In the case of having your legs kicked out as an outcome of a Saving Throw gone bad, the player recognizes that they suffered a setback and recognize their task is now to get out of a bad situation before they can proceed with weening down the monster's hit points and winning the encounter. The bad roll resulted in an opportunity to overcome a challenge, and that is presently more exciting than the hacking & slashing. Not necessarily so in a math game, where your goal is to overcome the encounter rather than have an engaging conversation about fiction.

If this situation does happens in play, seize the initiative and make a move. I'd agree that the correct GM move is indeed Tell them the requirements or consequences and ask, as Sage says, or maybe Offer an opportunity, with or without cost:

"It'll be hard to get in a good hit from where you're laying. If you want a good, clean hit you'll need to get on your feet first, but he's stomping and slashing at you - you'd need to Defy Danger to do that. If you really want to swing wildly at his ankles, you may be able to get him to give you a berth wide enough that you could stand up unharmed, though. But it won't be a hack & slash move that deals damage."

or simply:

"You hack wildly at his ankles but he simply laughs and hops away. He gives you a wide enough berth that you can get up and dust yourself off though, before he comes at you again with his broadsword raised high above his head... what do you do?"

In the case of no prior setback but established fictional difficulties (such as strong winds etc), in a modifier-driven game the player doesn't say "Well, my bow arm is so awesome I'm sure I won't get any penalties, so I'll shoot anyway", they say "I want to try to take the shot anyway, what's my difficulty modifier?". In DW/AW, this "difficulty modifier" is captured in Tell them the requirements or consequences and ask and the move they make. They'll say:

Player: "I'm going to try to make the shot anyway."
GM: "The winds are very strong. It's unlikely you will hit. You'll have to take a very steady aim, and that means you might lose track of the rest of the orc patrol."
Player makes a Volley roll, gets a 10+, deals full damage.
GM: "Wow! You spy the arrow zooming right in on the target. You hear a chunk sound with a subsequent squeal carried on the wind and the orc drops in the distance. But in the interim, you've lost track of the remaining orcs. What do you do?"
Or on a 7-9:
GM: "You have to shift a bit, leaving your hideout, to make a clean shot. But you hit! The orc drops. When you look up though, you realize the other orcs have wandered into your territory. They're almost upon you, though they may not have spotted you yet. There are a half dozen of them and they wield wicked, rusty blades. What do you do?"

You haven't penalized the player exactly for trying to make the shot regardless of strong winds, you've put them in a more interesting situation than they would've been in if the winds were calm and it was an easy shot. The player accepted the additional complication and got a chance to shine. Win win situation.