I'd be more worried about latency on a USB sound card than anything else...

I'd be worried about damage done to the card by clumsy fools who might come into my room and poke at it.

*poke*
Oops 😀

The USB products are pretty good, as long as you don't want to game with them 😀 The CPU utilization is horrible with them. USB of course is the culprit as it's just bad bad bad for the CPU. They are ok until the number of sound channels starts shooting up like it will in games, and if you use EAX or DS3D as they are all software-based.

http://www.xbitlabs.com/articles/multimedia/d … tive-sbmp3.html
http://www.extremetech.com/article2/0,1558,1473855,00.asp
http://www.extremetech.com/article2/0,1558,14302,00.asp