I have experience on the Fast Track Pro, it worked well on its field. Don't know if there's any actual difference between the Pro and the regular Fast Track, except that Pro has two inputs and midi.
It seems that E-Mu USB interfaces has better DAC and ADC than most of other USB interfaces (and E-Mu does not hiding this information).
E-Mu 0202 USB have exactly one mic input and one instrument input, but lacks balanced IO and phantom power (for condenser mics).
Tracker Pre has missed features. 0404 USB adds midi IO and digital IO and has better DAC.
I actually use the E-MU 0202, it's really not bad...
the preamps pretty much suck though, really noisy, but the "goddamnit-i-need-a-better-interface-moment" came later than i expected