One thing I dislike is that the maps are so few. I'm getting very tired of the two or three city ones... all the same choke points, all the same places that are nigh impossible to get through.
On the subject of camping, this is not an invalid strategy. Holding a position or thinning out the ranks of the enemy who pass through that area is completely valid. I have yet to see a place where you could not get to a "camper", you just have to adjust your strategy. Go a different way, or kill the person doing it. It's a point of realism that you can't just run around sprinting at random and firing from the hip and do well.