How do you do this, Vincent? Do you always have the player choose the improvement right then and there?
Because I see a few weird cases:
1. We're in the middle of something, and we want to keep going, figure out the best improvement option later. Let's not stall the game!
2. We like to have improvements come organically out of what's going on (like in The Shadow of Yesterday, where this experience seems to me to be derived from), creating interesting situations and revelations in play.
(I like doing that kind of thing, like when I pulled off a cool trick in this game:
http://apocalypse-world.com/forums/index.php?topic=1931.msg12482#msg12482)
3. There's an improvement we're thinking about, but the fiction isn't ready for it yet (e.g. gaining a gang), so it doesn't feel like we're quite ready to go there. For instance, a character is about to go meet a bunch of savage biker nomads to negotiate with them, and hopes to sway them to follow her. She gets an improvement and we all go, "Cool! Maybe they'll become your gang!" And the player agrees, but she says, "Well, let me meet them first, and let's play to see what happens."
What do you recommend?
(I find it interesting that Monsterhearts makes this explicit: you cannot gain any more experience until you've chosen an improvement.)