Great FPS-shooter, fantastic graphics, you feel like being in Middle-East or Russia, but it's only a short dream.
One big negative point is that indeed the single player campaign is very short. Just as you get the hang of it, it's already done. I think I outplayed the campaign in 7 or 8 hours, which is very fast taking into account my skills.
I didn't really try out the multiplayer yet, I had some tries with the free deathmatch, but it's quite frustrating. Before I know, I am already dead and the other players are continuously jumping around and moving a lot faster than I am capable of. But there are a lot of possibilities, so I will for sure explore it further the coming weeks.
But, summarized, certainly a great game and will not be the last COD-game in my collection.