If anyone's still looking at this thread, I bought the Tascam us-1641 as a Christmas present
and I've been recording 13 channels simultaneously with our band at rehearsals twice a week with no problems. The only glitch I've had is sometimes after a take I have to unarm the inputs or audio drops out. Not a big deal and the preamps don't sound bad. So, I say go ahead and use USB 2.0. For $290 (after rebate; including shipping) you can't really go wrong!
Rick