I don't see why people think he needs to change his racket. It's not his bad foot work, at least not entirely, it's the fact that he's aging. It happens to everyone, the great ones won't dominate forever, it's the same thing that happened with Sampras, Agassi, and every other great tennis player. Eventually, everyone starts to slow down, and it appears such is the case for Federer...
All aboard the Gulbis bandwagon!