Man this game is awesome, you really need to know where to go for cover and where your man need to be place for each encounter.
Also shot outs are the best when done correctly. Play with a friend thats even so much better. Timed shot are the best. hehe :)
I love the exp points system A.C.E its not new in games. It sort means something to take someone out by a headshot or you use your smoke grenades and shoot them under cover.