I think it's a new paintjob, but I'll have to ask him. It's actually possible that he did switch if it's true that he worked with Prince to develop the racquet.
If you look closely at his forehand, you can see that it's not really a true two hander, like Santoro's, because he only has 2 fingers and his thumb on the racquet. It is an odd stroke, but it works for him because he can disguise it so well. Of course the down side is that he has less reach on both sides and his footwork is a little suspect lately (I think mostly because of nagging shin soreness). I love his backhand though, when he can set up for it he can hurt people with it. Like Andy and others, he kind of twirls his racquet as he's moving so the grip changes aren't that big of a deal. I think it's more of a liability when he's at the net. But I haven't seen him play much this year either, so I could be way off.