The game is a good deal of fun, if you don't care about the completely irrelevant storyline.
My main issue with this game is the storyline, which pretty much seems to go nowhere fast. I will not mention any spoilers, but by the end of the game, you will have twice as many questions, and not a single one of them answered.
The other issue I have with this is the lack of horror in the game. Of course it has it's moments of trying to scare the hell out of you, but they did not do near as good a job as they did in EP. The bigger focus of the game seemed to be based more on combat, as they added a couple more weapons and new enemies to test them on. The mercenary squads are always fun to fight as they will throw out turrets and prox mines on occasion. Unfortunately with this, the AI has not been improved any bit at all. That's not a huge deal though because it's already pretty good.
There are some new enemies that you don't face very often, which is probably a good thing because they are ridiculously hard to hit with any weapon, and really just get on your nerves. This isn't necessarily a bad thing because it makes the game more challenging then the previous installments. They also seem to throw the heavy armored guys as well as mechs at you just when you seem to have no good weapons, little ammo, and not much health.
On the plus side, the game pretty much matches the length of the original FEAR. The new weapons, like the lightning gun, advanced rifle, and grenade launcher are definitely fun to play with. The battles are always fun, and with the graphics and physics, you can never stop having fun tearing each room into shreds as you mow down enemies. To add to this, they also added three bonus missions you can play after you finish the game. Honestly, they seem pointless to me, but if you still haven't had enough of the fighting, this is for you. They're like challenge missions, just go from point A to point B on various difficulties, try to beat your old times, etc. One of them just puts you in a small outdoor "plaza" and just releases wave after wave of enemies for a while.
Overall, if you're looking for a game that has any relevance to the original story, just wait for Project Origin, because the storyline in this is quite pointless. The combat is slightly improved with new enemies and weapons, and will last for hours as it's pretty much the only thing you will be doing. It's disappointing, yet still a fun game and definitely worth playing. After going though this, I just hope Project Origin ties the loose ends together...