This game has surely set a new high for all First Person Shooters. Highly addictive, and great fun.
Most likely the biggest disappointment is how short the game is. I managed to beat the campaign on hardened in around 8 hours or so. Others have finished it faster, but this is still rather short. The story also seems quite separate from multiplayer. The drama from the story is quickly lost when you start playing multiplayer, and the short stories impact is lost rather quickly.
If your not really into the multiplayer, then you also have the Spec Ops missions to play. These are actually quite fun when you have a friend over or are playing online. The missions have just enough challenge in them to make them enjoyable, and its great fun to keep trying to do better if you fail once in mission. Having the selection of missions to unlock is something that will keep people up trying to unlock it all and get 3 stars in everything.
Once you can proudly say you've beat it all you can dive into the fast and intense world that is the multiplayer. Here you get to level up your account enabling you to use better weapons and upgrades for them. The multiplayer also gives you a choice to play normal team deathmatch along with capture the flag, search and destroy, along with others. There is also a version that gives the player the ability to play in 3rd person mode, which adds a whole new feel to the game.
Overall: This game has lots to offer. If you are a hardcore First Person Shooter player then by all means this game is for you. If you enjoy a good story, but are less likely to play online then you should give it a try, just for the story, and you should give the online play a chance as well. This game adds a lot of entertainment value and replayability. You'll get lost in this games online play and amazed by the campaign's story.