A truly fun game, but maybe short on content.
On the downside the games campaign is not very long, though thats a complaint that could be leveled at most FPS released. That bigger issue is the lack of any competitive online. The online consist only of a Horde (as in from Gears of War) type mode where you can team up to wreck havoc on the enemies. This mode works well, and I'm sure some people will play it for dozens of hours, but it doesn't appeal that much to me.
Overall, this game is a perfect rental for most people, it's a good buy if you just don't have time to beat any games quickly even if they are short, or if you are a fan of games with co-operative play against non-player opponents.