i spent a few hours the other day trying to get ableton live to do sound on sound looping, like the boss giga-delay. i couldn't find a way to get it to work. so i sent of an e-mail to the clan analogue mailing list to see if anyone there knew a way of doing it. a few different workarounds were suggested by people, but all, as workarounds do, have their limitations. then, this morning, someone posted a link to this - http://www.ableton.com/pages/live_8/announcement/looper. needless to say, i'm rather excited at the prospect. though it will, of course, require an upgrade - are you in, steve? it's due in the second quarter of 2009, according to the ableton website.
as a result of finding that info, i also started googling for something along the lines. so far, this looks the most promising, but i haven't had a chance to try it out yet.