Frustrating and completely lackluster singleplayer, yet very fun multiplayer.
Equipment is earned in SP by earning stars. You get them from your rating on different missions. You also need medals to level up past a certain rank. These medals are mostly dependent on luck and memorization of all enemies in a particular level. This makes them more rewarding, but it grows tedious to try again and again. Medals are terrible in multiplayer. In the heat of battle, how are you supposed to kill 20 guys with c4 or grenades,(?!) let alone kill 4 people with a knife (?) in one life(?!).
On to the real meat of the multiplayer. The maps are vast and colorful, and at the same time hard to see enemies. The sniper rifle is EXTREMELY unbalanced, so if you hate people n00bing you then you WILL NOT like this game. The convenient hiding spots and huge sniper distance do not help.
Here's the real good stuff. It is fun to get in tanks/helicopters/other vehicles and blow **** up. It is also fun to rocket n00b random people who get too close to your base. And it is also fun to team bleed with the pistol since it is next to useless. My personal favorite, "c4 the helicopter and then TK anyone who gets in it" never gets old.
The bottom line is that you should not get this game unless you are a hardcore military shooter fan/ multiplayer military shooter addict, or just want a tactical multiplayer without expecting any achievements.