Just to add my 2cents to this thread, I've been developing a live performance application for Linux which I have used in several shows.
It's called LoopDub and is really just for mixing loops. So far it's not super user-friendly, but it does the job I designed it for. It allows to load 8 loops and then load other loops in the background, and switch between them on beat. It can be completely controlled via MIDI so I could conceivably just close my laptop and stick it under the desk when playing (except that I tend to forget which program is which, so I need the screen..) I intend to add more methods for modifying the sound live and whatnot. So far it just has some built-in filters and echo. The CVS version has several improvements, so watch for a new release soon. (I'm too busy with school at the moment to work on it but summer will see the next release for sure.) http://loopdub.sf.net Steve