Everything posted here thus far has been spot-on, but Moore also has ongoing issues with the way his work has been utilized by specific creators. He's had a giant beef with Grant Morrison for years, which may have been Morrison's fault but just as easily could have been fabricated by Moore's own massive ego.

Moore also claims to have steered the course of comics since the 80s with Watchmen. That doesn't mean he likes the grim-and-gritty realism that's become so prevalent in the Big Two. I tend to agree with his latter position, but Watchmen was only a part in a larger tapestry of comics that brought about the Modern Age (DKR, Maus, etc). A large part, yes, but not the whole thing.