The new challenge system adds a lot of depth to the game. And the story of F.E.A.R. continues, better then most movies.
Sound: I cannot comment on the music, I always turn it off. I like to game in the dark with surround sound going to get all the scratching and growling I can! Some of the AI comments do get repetitive, such as "He shot my arm off." Probably the last thing I would be saying if my arm was blown off. But overall the sounds fit the game genre and environment quite nicely.
GamePlay: With the addition of the 'Challenge System' you pay a lot more attention to how you are killing the baddies. I like how it carries over from SP to MP and leveling up is quite fun. Shooting feels natural and fluid. I'm not overly impressed with the grenades, as one friend said the AI seems to throw them constantly and when you do they do little damage unless they are right under the baddies butt. But other then that the gameplay is some of the best I've had to date.
MP: Quite and different from other games. You have to try it to see what I mean but it is definitely a good time for all.
Replay: Unless you are an awesome gamer, I'm not at my age (near 50) I have to play through once to figure things out and then go to Insane so I have half a chance of beating it. But you 'll need to play through the game multiple times to max out your level or play a lot of MP. Nonetheless you'll get more then one play through with this game, it is just that entertaining.
Buy or Rent: As a fan of the series I bought it. A good gamer could get through the single player campaign in a day (on Commando for sure) and the do some MP for the rest of the rental period. I would suggest buying it though, great shooter to have in the old collection.
Overall: I say 8.5, the game will take you on a great journey with excellent graphics, sound and gameplay that you won't soon forget or regret.