Hi Greg
I use the Fast Track Pro (USB1.1) daily without problems - it has not been switched off for about 3 years now - very low latency as well. It works very well with PG's products (and others). I record vocals and guitar etc and it is rock solid stable (must also be the drivers as Mac indicates and M-Audio are on the ball and update when needed). The Ultra looks good but do you need so many inputs/outputs? - personal choice.
Roy, Pretoria, SA