I've integrated looping into my show pretty severely at this point... I'd say it's do-able to use loops in ensemble playing, but it's definitely easier as a soloist... the biggest problem with using loops in a group is making sure each player hears the loop loud enough... if not everyone is feeling it, then not everyone will play to it.
As for gear, everyone's feel is different, and so is every looper I've tried. The JamMan responds differently than the Boss Loop Station (which I use), and both of them are very different from the Line 6 gear.
The best looping gear I've ever seen is the "Looperlative" unit. Google it; it's absolutely ridiculous! :shock: