Fixes all the issues that were in multiplayer on MW2. But has a few issues of its own.
Multiplayer: Which is what basically everyone brought the game for. It is extremely fun and feels much more rewarding to play than in MW2. Trayarch did well in decreasing grenade launchers abilities and removing commando and one man army. It is highly customizable with the addition of CoD points, letting you buy what you want, when you want. another fun addition to multiplayer is Wager Matches where you can wager the points you've earned in game modes. Theatre Mode was another smart addition to CoD. If you've ever thrown a knife across the map and wondered how it killed them. Well now you can check. With the ability to pause and free roam your played games, this was another great idea from Treyarch
Cons: Trayarch takes a step back with the graphics in this game. (Unless its because im playing on a crap tv) They seem like a tie in between ps2 and ps3 graphics. The sound is also another issue, with some noises sounding fake and muffled or because you can't seem to hear enemies online even with Ninja Pro.
Overall the game is still definitely worth buying, unless of course you're one of those cocks that goes 'OMFG THIS IS DIFFERENT TO MW2 GTFO" Then you can go die in a small ditch.