One of the "problems" I have with RSS is that it seems to be a lot harder to watch a thread.  Perhaps this is mostly a client issue (I use SharpReader), but I think it also has to do with the different comment schemes and what really constitues a change.

NNTP is also valuable in that has mechanisms to efficiently distribute content (everybody doesn't have to hit your website).  Not to mention that NNTP is better defined than all these different versions of RSS.

Maybe ATOM will be the "grand unification"...