Murray got a bit lucky there, because the format was bo3 till the final, not bo5 like a GS, Roger was completely gassed out from the Del Potro match (showing that he's still aging regardless of what people say

), he completely deserved that gold medal but it cannot be compared to a GS win, having to play Djokovic and Federer back to back in a bo5 setting would be really difficult.
One of the things I've noticed about Roger in this US Open swing is that he's not brainfarting, he tends to get a bit complacent and walkabout for a set in most tournaments if he's having an easy lead, in Cincy and the USO he's been brutal, rarely taking off his foot from the gas.
BTW Roger is now 23-0 lifetime at night in the US Open, those conditions definitely suit him.