If you have the money, the Duet is an amazing little (tiny, actually) portable device. You can control the unit directly from inside of Logic (and GarageBand) via CoreAudio. At five benjamins, it is 2 or 3 times more expensive than some of the cheaper USB audio interfaces out there. But IMO the improved fidelity and uber-low latency (mic'ed or direct) makes it worth it, even at twice the price. You'd have to demo one side by side to the competition to really appreciate the difference. It may not quite be an Ensemble, but it is still very much an Apogee. Absolutely perfect for the mobile musician.
does it have phantom power for the inputs>? how many mic inputs can u use simultaneously if i wanted to record a drum track?