This overview video helped me get an idea of how to work with it -
http://www.youtube.com/watch?v=jW05NcfGxO0 Towards the end of it, there's a little demo of how to use it as an effect, and I've messed around with it that way, with loops. Basically, I'd get a loop going, and then play with using R-Mix as a sort of live mangler/effect/filter. Depending on the kind of loop, and how creative I felt, the results could get pretty darn interesting. Doing an automation record while you play gives take lanes for the various parameters, which then can be edited. Seems like there's lots of potential there.