The more videos I see of this game the more I want to play with it. Not only is their always some cool new feature (ion blast weapon, new races etc.) but there's lots of little additions (that I imagine aren't so little to implement!) like new animations and the dynamic music that help to add something extra to the game. Looking forward to getting my grubby mitts on the beta and I echo everyone else's view that you guys should take as long as you need, the more time spent the better it's going to be.
Using different races to encourage different playstyles definitely seems like a much better way of mixing up gameplay than player customisation, it was always going to be nigh on impossible to keep balance with that sort of thing (though it might be cool for a sandbox type mode, I doubt I'd play it but some people like that sort of thing). In terms of different races altering gameplay I think it's definitely worth taking a look at the Desktop Dungeons Alpha (
http://www.desktopdungeons.net/media/) handled it (not sure if things have changed in the beta, I Imagine not) as it's exceptionally well done. The early available classes all serve you well as you learn to play the game and the later classes you unlock are generally a tad more challenging or require unique (and more importantly fun!) tactics that perhaps require advance knowledge of the game. Indeed many of these unlocks are only availabe after completing particularly challenging tasks. It's a good system, especially as it allow the player to continue to be rewarded after many playthroughs. Of course it might be tougher for something like this to be added to FTL as it's a lot heavier on art/animation assets than the likes of Desktop Dungeons and I doubt the devs would want to spend lots of man hours on good work that a lot of people might not even see!
Anyway, loving how this is shaping up. Looks fantastic, definitely one of my most anticipated games this year.