Frustrations made me uninstall before I even got to the end.
The quest system still needs work. Sometimes I would walk into a zone and get a quest without talking to anyone. Then if by magic I would complete it without doing anything. Some quests were broken too. Also the same quests would be available over and over. I'm not sure if that was planned or a bug. If it was planned it was not a good plan. Redoing old quests is lazy game writing.
One quest that was annoying was when I had to "infiltrate" a small base to get some documents (which is all you do in the main quests - I felt like a Delta Force secretary too much of the time). The guy told me to sneak in at night because there were only supposed to be 2 guards after hours. I could get in and out without calling down the military's wrath on him and his camp. I got up to the base and started a huge fight with everyone aware of my presence and gunning for me and the loud speaker yelling about me being there. After I killed off the whole base I got the docs and went back to the guy, and he said thanks here's your reward. He never mentioned that I made all hell brake loose. Another thing that was odd is after I killed everyone there the loud speaker kept screaming. I'm not sure where that guy was who was on the mic. Which is probably good for him cuz I would have killed him too.
The escort quests need help too. When you have to protect the scientist while he tries to get back to the mobile lab after the helicopter crashes, he says that he isn't a good fighter so you had better go first and he will follow. Then the butt-munch takes off running as fast as he can. WTF?!? He does the same thing when you have to follow him while he gets readings later on. All of that was more annoying than anything else. What ruined the game for me was the aiming. At the beginning of the game it isn't that bad because the enemy's armor isn't that strong, but when you get to the more difficult baddies, where you have to head-shot them, it is downright frustrating. I got sick of having my scope dead in the middle of a bad guy's face from only 20 yards away while I am squatted as low as I can get, and I still can't one-shot him. I could not tell if I was just hitting armor or missing him altogether. It would have been much better if the game made the barrel sway instead of just randomly deciding whether you hit the target or not. Play Farcry if you don't know what I am referring to. As a matter of fact just play Farcry. I feel much better that I have gotten all that off my chest. The game had some strong points, but it felt like a beta to me. Maybe they will figure it all out in the sequel.