Oh, I don't know if he's a fanboy or not or how much of his work he likes. But from much of the things he's said, of Whedon's work he liked Angel. I've never got the impression he cared for BTVS or Firefly to a great extent. Sure, he gives the standard "I'm a big fan, blah, blah" you always gets, but the tenor of his words in commenting on them doesn't really back it up.

But yeah, he knows he needs Joss more than Joss needs him.