I can't see him winning countless Grand Slams, but he is good enough to win the odd one here and there. There surely cannot be any doubt about that? Whether he actually goes on to do it is another matter. Personally I see more shots in his game than I did in Henman's, and I was a Henman fan. He is a very talented player. He isn't as good as Nadal or Federer, but I don't think he is a million miles behind Djokovic.
The physical side has held Murray back. He had fitness problems, though he seems to have dealt with them now, and he hasn't developed as quickly physically as the aforementioned players. Partly that is his genetic make up, and partly that is his own fault for not having a properly tailored training regime. But that is another thing which he seems to be trying to combat.
Murray will be a force. I have heard nobody compare him to the likes of Federer, Sampras and Borg, and I would laugh at them if they did so, but your personal dislike of the lad seems to be getting in the way of any objectivity when it comes to his sporting prowess.