I haven't looked up comet into detail, but I suppose it is using Server Push, which was described in the first CGI book I ever read, 13 years ago. There is the problem of realtime updates with AJAX, and of course that Server Push odditiy has come to mind several times when I discussed it with friends. Maybe if Comet pulled it off in a proper way, it could be rather cool. However, ultimately it would also be a hack of sorts, which gives me an uneasy feeling about basing my business on it.

Sorry for the uninformed blabbling, I just wanted to challenge the "community has never heard about it" stuff - at least I have heard about it, sort of, but I did not yet consider it the next killer application.