Hellmuth is a great player - I just skimmed through his book last week and he offered some good pointers I will incorporate into my game.
As for his personality at the table, I understand from what I have read he likes to talk a lot to distract his opponents which is fine. But I saw a few Youtube videos of Phil chiding other players at the table. As a professional poker player, he just does not act like it. All the other pros call him a "brat" which from the videos, he clearly is.
But it comes with the territory. I mean, look at other sports:
Phil Hellmuth : Professional Poker :: Terrell Owens : NFL