The popular notion isn't that Subversion sucks, but that it's pointless. The claim I hear is that it's a reinvention of cvs, but it doesn't actually improve much. Personally, I had to learn cvs, it's simple enough for my needs, and I see no reason to switch to something that's fundamentally the same thing.
I think most cvs users are in a similar situation as me. We know Subversion is better, but those benefits seem marginal and not worth the effort to switch.