Why on earth not? He's an excellent director. Have you seen A Simple Plan or The Gift? Don't judge him just because he's famous for ghoulie films. (Which, by the way, was the only thing Peter Jackson had ever done before LOTR, and look how he turned out.) Don't knock horror films - directors that do those learn an enormous amount about filmmanking in a very short time, and those films teach them to handle FX and CGI better than just about any other type of cinema.

I'd be a lot more leery of some Serious Dramatic Filmmaker or some guy completely puffed up with his own success (like Scott or Spielverg) than of someone like Sam Raimi, who has both the chops, the sense of humor, and the hunger to pull off something like The Hobbit.