Good game - not the best.
The atmosphere of the game fits the plot well, the computer A.I. isn't bad, the RPG elements are great, the puzzles aren't hard enough to figure out that you need to resort to a strategy guide, the architexture of the levels are quite impressive, the overall graphics are very nice, the music fits the game well, the sound effects aren't bad, the weapons are fun to toy around with, towards the end the story becomes extremely exciting and the multiple endings are a great addition.
The storyline is rather unoriginal and extremely predictable - who didn't know the truth of everything by the end of the second mission? While some of your actions can change the course of the plot, it doesn't change it enough for you to notice or really give two hoots. Too many of the missions they make you go through involve crawling through vents. Most of the quests you must go through have very little to do with the storyline, and you'll often finish a quest thankful that it's finally over and you can get back to the storyline, only to have to go through another pointless quest, and then another, and then another. While some of these quests aren't that bad, I was more interested in the advancing in the story than shooting up some bad guys and crawling through vents.
The Bottom Line
I thought the game tried to include too many standard shooter elements into what really was a great first-person RPG. The game is worth your money, and a blast to play through, but you'll get quite frustrated at times being everybody's errand boy instead of the hero. It's one of the better games I've played, but not as good as I had hoped it would be.