I've been using an M-Audio C600 interface for over a year now.... LOVE it. In fact, I just finished recording an album with it.... I know it sounds funny, but seriously.... it was that reliable. The only thing that was irritating, and I don't think it was even the interface's fault, was that if you unplug the USB cable, you'd literally have to reinstall the driver. REALLY irritating. But, I think that must be a setting within Windows that can be changed. I just haven't found what that setting is yet!
On another note.... I also have an M-Audio Keystation 88 controller that I also LOVE. M-Audio makes great stuff.