It's possible that Bin Laden is hiding in Iran or Pakistan and in order to get him the U.S. would have to take out one of these countries. So what is the priority?
It's possible that Bush and the CIA know Bin Laden's whereabouts in Pakistan or Iran. Should they attack and put boots on the ground? I think it's better to wait for the opportunity to snatch him on the cheap.
I've no doubt they know where he is and have done for a long while. There was plenty of opportunities at the start. Its amazing what one man and a donkey can escape from. No better time than the present. With such a powerful army and backing from the tea drinking Brits I'm sure his capture/murder is very achievable.