I don't really understand the poor reviews of this game, which is, after all, an expansion. Just because it is standalone, does not mean it should be something completely different from the original. It is gimmick-free, stable, highly playable and action packed.
A lot has been said on this game's engine, that it is now dated and not as good as newer games. Fair enough, but it's still a decent engine, which I've had running smoothly on Vista on full settings at 1600x1200 with no slow-downs or stuttering.
This episode is different from the others in that you play a new character with apparently similar talents to the original. There are new weapons and new set of bad guys, and the action is relentless. If you liked FEAR, I believe you will like this game.
Having said that, this episode gets you exactly no further forward in the story than before, as for most of the time you are acting out events in parallel to the other two episodes. I'm looking forward to Monolith's continuation of their part of the story, in addition to Sierrra's future episodes (Monolith left Sierra's production, but Sierra has kept the rights to the FEAR name).