I just got this game a few days ago. I have been extremely disappointed with the multiplayer, but I'm not even sure if it is the game's fault. I managed to find a pvp server with enough people in it and had a good time, but eventually the population dwindled and it got boring.
I see there are tons of coop server with low pings and high player counts; but there are only like 2-4 pvp servers with pings less than 100 to me and they are almost always empty.
I bought this game because I wanted a really challenging and realistic experience, and the AI is the most unrealistic part of the game. You can't snipe them or use stealth against them because they always know exactly where you are as soon as you shoot at them, even with a silenced sniper rifle from long range. The AI can uncannily detect you even when you are moving through dense forest.
I think the game has beautiful graphics and mechanics, but it really goes to waste when I can't find a server where I can play against real people.