Yes, Ive noticed he's more comfortable and relaxed since he won his 1st slam and he's developing a better style with the media. Smiling, joking etc.
Its no wonder though is it? No one can ask him "When will you win your first slam?
I think it's because in winning that first slam he made peace with himself. By wining Wimbledon he made peace with the Great British Public.
Now he has sorted his back out, so much of the pressure is off him. He can relax and enjoy his tennis now. Constant pain is incredibly draining. I also wonder if the fact that nobody including himself, is really expecting him to win this year also means he can be a bit more laid back.