I've never used it, but it's a fascinating idea. The quirk is that no two participants, assuming they're each actually playing and not just listening, will hear the same thing. The following things happen simultaneously:

* Alice will play for X measures, while hearing what everyone else (including Bob) played X measures ago

* Bob will play for X measures, while hearing what everyone else (including Alice) played X measures ago

So for the measures mentioned above, Alice might conclude that things went very well, and Bob might conclude that things didn't jibe, and even if these were each true objective facts, they could both be correct as they are not discussing the same thing. There can be no retrospective discussion of a shared experience, only of individual experiences.