C&C has kind of a history which still influences attitudes about it. There have been personality conflicts, flamewars, a lot of bruised egos and pent up passive-agressive behaviour (you can see it in this thread if you wish). C&C has attracted this sort of thing in part because it assumes a lot about the nature of roleplaying games which are antithetical to the current consensus. For example, it has a different attitude towards DM (or, uh, CK) authority, what the rules are supposed to accomplish and what a system needs to model than what is fashionable. Then there is the whole "rose coloured glasses/nostalgia" argument, the annoying proselytising by overeager fans (as another example, Scarred Lands comes to my mind), and the fact that the development process left a fair bit of people dissatisfied. A lot of self-proclaimed grognards take a very dim view of the game, much dimmer than anything I have read on ENWorld.
Myself, I started with the basic box as a baseline, and built a game of my own on top of that. It is no longer really C&C, but I must be thankful to the TLG people for catalysing my thoughts. The support material has been a bit ho-hum, and I am rather frustrated with the direction of the Castle Zagyg project... but the game itself is pretty solid if you would like a lighter alternative to D&D.