I have watched couple of matches Djokovic played at the Dubai,one against Del Po and the final against Berdych, and his level of play this year is amazing so far. His forehand is a weapon, he doesn't miss a backhand, his return of serve is beyond belief, serve has gotten much better, groundies are deep and consistent on both wings. He appears calm even when he is down a break or set, and he can play long 5 setters if he have to and grind it out and wins almost all of them.
At this current level of play, can any one stop him at the majors this year? It would take a phenomenal effort to stop him IMO.