For me at the moment it's 7057 x64. No problems so far, running all games (including ones that Vista didn't like!). The only thing is that because of the funny 'birdy' login screen and the desktop.ini issue, always makes me think that there might be something else that's not quite right, but I just haven't found it yet! Probably a self-destruct thing somewhere that wipes your hard drives or something! LOL.
The only reason I prefer to run this over 7048 is that the expiry on this is March next year. I know you can get cracks or whatever, but I don't want to mess with them. After all, I want to be testing these builds as they are given (or leaked) to us from Microsoft. That way I can moan if something goes wrong!
REALLY looking forward to release day, I'll feel proper chuffed then! (I hope!)