Oh my god. Just finished Far Cry 2, and I have to say that I have never been this surprised by a game like this. I went from not liking it, to starting to like it but being frustrated, to now loving it. This is only behind Fallout 3 for Game of the Year 2008. Some thoughts.....
1: I hated the guard post re-spawning so quickly. I understand that they would eventually replaced dead guards, but it would have been nice to do it in say a 24 hour period. That being said, I found myself playing the game differently. I would drive out of the way to avoid known roadblocks, especially late in the game when they started having rockets that would kill you in one hit. Even if you wanted to play this game balls to the wall, you still had to play a bit of stealth from time to time. So in a way the re-spawning made the game more edgy.
2: I am surprised this game did not get more attention for its graphics. I really did not see a game this year that was as breathtaking. Far Cry 2 was gorgeous, with huge vistas, no load times (except saves and bus travel) and the day and night cycle, along with dynamic weather, fire and other effects, that never let up. Grass and trees, unlike the Call of Duty 4, looked real. This game proves that you don't need 60 frames per second to impress. Only minor pop up I could see.
3: Loved loved loved the ending. It felt like the beginning of Far Cry 1....did anyone else notice that? I wish the ending was a little bit harder. Heck there were some guard post that I had a harder time with.
4: Enemy AI was so good at times that when it messed up it was a bit jarring, but there were things they did that really surprised me. I did not like their GOD like vision in the jungle, and their ability to fight indoors left a lot to be desired, but nothing will get your heart racing more in a fight then when you hear that sound of a car engine growling up and you know you are fixing to get run over.
5: Jamming enemy weapons you pick up....OK, but come on, within 5-30 shots? It sure seemed that they worked better then that for them. Jamming weapons that you buy after 2-3 missions?

realism, when you buy a weapon it should last longer. Not a big deal, as you get in the habit of running to a gun shop and replacing them, but just a small annoyance.
If you have not played this game do yourself a favor and pick it up. If you have only played this game up to about 40% or less, and gave up on it, stick with it. Change your play style, and you may find you love it. I would have given the game a 6 out of 10 at the start, 7 out of 10 about 35% in and ultimately a solid 9 of 10 at the end.