In case anyone looks at this thread, I'd better mention that it seems that using CCRMA's distribution fixes my audio problems with the Behringer UCG102.
I had been using the standard "Raspbian" distro when I wrote my comment. I believe that distribution uses a different kernel than Satellite CCRMA, which is optimized more for embedded audio projects.
I had been unable to do duplex audio at 44100hz (had to switch to 32000), but now it seems to work fine (even when running pd with an X11-forwarded GUI). There's no noticeable dropouts at a latency of 10ms, at least in my initial testing!
In order to get this to work, I simply had to change the text of /boot/cmdline.txt to the text politely included in /boot/cmdline-usb1.1-only.txt (thanks, Stanford guys!)
Anyway, just hoping I haven't led anybody astray from the Pi with my earlier (somewhat misinformed) comment. I'd still be a little wary of using devices with more channels or without linux drivers.
-Brian