The PC version looks better than that. It's obvious that gamespot had some settings lowered. They definitely didn't have HBAO+ and Soft shadows enabled.

Bungie had already said this was the last of the Halo series -------------------------------------------

There hasn't been any optimized drivers for Vista yet, of course it will be a bit below in performance than XP. Not to mention, Microsoft said that DX10 was supposed to improve performance for gaming. I never heard anything about DX9 having the same benefit on Vista. People just need to be patient, allow the OS to mature.