I've recorded nearly 48 hours in BC2 MP so far, and this is one of the few games that I've played that actually gets better as you play it. It grows on you slowly at first, but as soon as you start piling on the unlockables, the game really takes off.
Seriously, those of you that don't play MP owe it to yourselves to at least try it out.
There is a learning curve though, so don't expect to be a godly player from the moment you start. In fact, in the first 5-6 hours of game time, you'll probably get your ass handed to you.