There are a LOT of guitarists using them round my area to 'capture' the rhythm guitar part during a verse or chorus, then they get to do a bit of a solo over them, then turn it off and go back to the bridge, or whatever section comes next, but few use them to build an entire piece, like this.

There's one very talented lady jazz singer/keyboardist that occasionally uses one to do some acappella things built up just using her voice... It's a very cool gimmick, but she only does it once or twice in a whole show.

There's a looper built into the new Roland V-Combo VR-09, so maybe this technology could get combined with the Chord Sequencer concept, and we get the best of both worlds... But I'm rather hoping that arrangers get a decent arpeggiator first!