This game has recieved a lot of attention and acclaim, and rightly so it is a decent game. However it is not that amazing (i.e 9.0 points is too high). From my point of view it is way too short to be worth as much as other "full" games. Also the enemy A.I is not terribly good at all and they mostly seem to try and beat you with sheer numbers, spawning behind you and being able to tell exactly where you are as soon as they come through a door.
Friendly A.I is terrible, as they fail to hit anything and just seem to walk into a hail of bullets (thankfully there are not too many times when you fight with others).
Another issue I had with the game was the mob wars, somewhat akin to Halflife where the aliens and marines fought little battles in front of you, except in MP2, everyone will stop gighting their battle to shoot at you a soon as you peek your head around a corner.
The story was O.K although the big twist was a let down for me anyway as it seemed a bit forced, (and I liked the character before he turned). The usual over the top noir type monologue was great as long as you were in the mood. I loved the physics scattering things with grenades and sending bodies flying was fun but nothing new.
Well I recomend you play this game, but wait for the prices to drop because the bottom line is 7hrs (at fairly leasurly pace) is not worth the full price!