Thunderbolt doesn't pull as much power as Firewire does. I haven't tested it out, but I don't think phantom powering a mic would work properly. Apogee also has been a bit slacking in the original Duet in terms of support, so I decided to get a new interface. I had an issue with my Duet when it came to scrolling windows real fast, and they couldn't figure out the issue. I also had a memory leak that would occur, but I was able to fix that myself by reinstalling the OS all over again. I could be totally wrong, though. Kinda hard to test when Apple hasn't released their freaking adapter yet...
Edit - And that adapter better be FW800, not FW400. I just bought a FW800 cable today for my RAID 5 setup to plug into the adapter for when it's released........