I dont know how different it is between computer and the Sexbox 360... but I own the 360 version.

This is honestly the most addicting game I have ever played. So many unlockable guns, with perks that you can use to help how you play. For example, there are perks with explosive weapons. (claymores, C4, RPG) There are perks with special abilities. (UAV jammer,extra dammage, extra health) And there are other perks. (Dropping a grenade at death)
Then there's the weapon customization... You can unlock upgrades such as Red Dot Sights and silencers. Also, ACOG scope (Takes practice, but EXTREMELY worth it when you get used to it.) And grenade launchers.
You get gun camouflages, starting with a woodland and dessert. You get more camo options as you get more head shots with that weapon.
Then, once you finally get to the dreaded level 55, you have the option to start all over in exchange for a noticeable icon next to your name.
Gameplay_______________
There are few downsides to this game. I can only think of two right off the bat. 1. NOOB TUBES (grenade launchers) They are used to get easy kills, and take no skill to use. I only use them when I have them used against me. 2. Random grenades... You'll see what I'm talking about.
People are very good at communicating (on xbox anyway)
The learning curve may seem steep at first, but once you develop some aiming skills, (and get that red dot sight) You'll be running into streets poppin' some heads.
The game is the most addicting game I have ever played in my life.