Yes. Even as a rookie, he really wanted stuff to go a certain way. I don't think he had a bad attitude at all, just very structured in his approach.
He definitely won't win "Most Engaging Personality" competitions.
Mussina is one of the smarter guys in baseball, and from what I hear from people who've met him, he's a really nice guy with the fans. I just wish he'd realize that when he talks about his routine being messed up, like with the Yankees' trip to Japan, he comes off as a whiny crybaby!