As others here have already predicted, I'm going with Federer in four sets.
That being said, I've got nothing against Federer, but I'll definitely be pulling for Roddick, 'cause I like him and I like an underdog. I think he's playing the best he's played in a long time, maybe the best he's ever played - but it's really tough to bet against arguably the greatest player that the game has ever seen.