It's like Counter Strike and Call of Duty had a baby, except whichever was the mother did dope during the pregnancy.
In other words, it's not very good.
Still, it's not quite horrible. You can still enjoy it. I certaintly am. Just not that much.
It's a mission-by-mission game with overly linear levels. Doesn't sound terrible, does it? Not very Counter-Strikey, but not terrible, either. The real problem is the combat. It does the Counter-Strike thing where your guns are only acccurate for the first shot, but now they do a lot less damage than they did in the original game, making combat a somewhat frustrating ordeal. It takes way too long to kill people, which, in a series about killing people as effeciently as possible, kinda messes with the experience.
Like I said, it's not horrible, but it just isn't Counter-Strike. I'll still reccomend it, because there isn't anything inherently wrong with the game. It just wasn't what I was expecting from a Counter-Strike game.