It has those "30 seconds" of fun that you can play over and over again!!!
The ability to play 4 player co-op over Xbox Live in the campaign is one of the best features in this game, it makes the campaign as re-playable as the multiplayer. Some of the achivements must be completed in a co-op campaign and and different skulls or game modifiers gives a challenging game to a person of any skill level.
Also this game finally puts the final balance between all of the different weapons. In the case that you have Xbox Live it will become highly addictive and lots of fun, between community content and all of the different game types this is a game you will play for a long time before you get tired of it. Making really good maps is not an easy task and Forge(Mode that let's you modify maps) does not help you, it just gives you the building blocks.
Besides this the whole game is a lot of fun to play, anyone who like FPS should give it a try!