White paid for aggressive early play with a lack of development, especially in the queenside. 5... b5 certainly did provoke him in to attacking, which just speed up black's development. I'm not certain if it is sound though against a strong player. I think white could have held on better from move 15 with d3, but would have to defend precisly to even have a chance.
Objectivity aside, this is the best game I've ever played... possibly one of the best games I've ever seen!
Maybe I'm just overzealous but this game was a LOT of fun to play.