PC IGN 9.4
GameTrailers 9.4
TeamXbox 9.7
On the 5 hours, Gametrailers I think said it well when they pointed out some of the additional SP options like Arcade mode and their advanced difficulties if you want to replay SP.
Arcade mode is complete old school NES style scoring. Time limit, combo streak scoring, limited lives, etc.
While 5 hours is short, the game has a pretty robust MP. 16 maps and 6 modes (TDM, Search&Destroy, Domination, etc) as well as gameplay modifiers like "hardcore" (which takes away most of the HUD and makes the bullets far more deadly). On top of that you have all the classes, perks, and loadout customizations within a fairly quick "rank up" system (unlike BF2).
If you are a SP only gamer, then this is probably a rental unless you really like what CoD does (and CoD is definately one of the better SP FPS on the market in terms of quality). But if you are a MP gamer at all I don't think there is even a question.
I know I am picking it up this week.