here is a small youtube of what they were made to do
http://www.youtube.com/watch?v=TVN9ges8Bo4
you could do some live loop stuff recorded off records,tapes, radio, etc and chop them up with the included effects. You could also use the s2k for throwing loops in a recording, like the way hip hop samples other songs
however I see no problems using it as a looper on bass, but you'd want to get a foot controller for sure--just something like a behringer FCB1010 or something.
you could also use it live for some weird in-betweens between songs if you want, but with only 11 seconds of looping, you'd probably want to upgrade the memory to 32mb for more time, or buy a lot of disks for various loops