As long as your players and yourself enjoy themselves I guess. But really if you don't last at least five-six sessions you might be doing it wrong. After that, things get huge - like cosmic-scale huge - and it's a shame to miss that part of the game.
My first and foremost advice is play by the book. Try to forget you have played other RPGs before and read the book as you would read any other rulebook for any other game, and when in doubt, refer to the rulebook. I know it sounds a recipe for disaster but that's not your daddy's Rolemaster. The rules are easy and sound.
For example, when I first MC'd a AW game, I didn't care much for MC moves. I thought "well, that's what I'd do anyway in any other game" but no. You get to do one move, maybe two when they snowball, but then it's their turn, and you have to wait for an opportunity to make your next move when the game allows you to, i.e. somebody misses a roll, a PC move tells you to or everybody's looking at you to say something. And that changes everything. Because it lets the players breathe and react without you piling up on them unwillingly. And it's not that restrictive, because the MC's moves aren't really about what you're saying but more why you're saying it in the context of fiction. I mean I could fill books with different ways of announcing future badness or inflicting harm.
Really, the more I MC that game, the more I stick to the rules, and the more my players enjoy the game. When something's off during the game, go back to the book and read that rule again. Often you'll find you were just doing it wrong. It's that well done.
Also, don't bother about fronts and countdowns and shit. Just follow the first session sheet, make the life of the players interesting - just by letting them do their stuff and hit with a move when they miss a roll or wait for you to come up with something - and take fucktons of notes. It's really all there is to it: barf forth your apocalyptica, ask questions like crazy, find non control zones and push there, name everyone and make everyone human.... Follow the list, the players will take care of the rest.
Also, Vincent really doesn't fuck around when he tells you not to pre-plan your storylines. Play to find what happens. That's what the game's made for. Try to push your storylines upon your players and you'll feel like trying to make chess a coop game.
Hope that helps.