> I don't remember people complaining about Winamp being a non-standard UI, but if it were slow then there'd be tons of complaints - and many of the "fancy" UIs were terribly slow (or the programs were, hard for a user to tell the difference).

Wasn't Winamp 2 the gold standard? I remember plenty of music lovers switching to foobar2000 when Winamp 3 came out, because it was, as you said, slow(er).