He advised against a strike until intel confirmed OBL's presence. IMO, he was concerned about invading an allied country without permission or knowledge and the repercussions of mission failure (e.g. many Americans and Pakis dead but no OBL).
The raid was a tough call by Obama but I believe it to be the right one. Results count, but there was a risk nothing would be there and the US would be guilty of invading an allied nation.
Consider that, had the raid failed, commie cocksuckers, Putinites and traitors like Dookie would still be whining about it.