I played the campaign and was hesitant to give multiplayer a shot, but after getting a multiplayer game in, I haven't gone back to campaign and have been playing multiplayer nonstop. Its been that much fun for me.
However, there are several negatives about the multiplayer: It is heavily bugged and somewhat unbalanced. There is little incentive to progress in multiplayer; other than the ranked games. But my biggest gripe is the randomness of squad selection. There is an element of pure luck in some matches where you will select gear for your squad that will give you a strategic advantage over your opponent's squad. And it works both ways, obviously. For example: If your opponent goes a mind control build and you just happen to guess and equip your squad with mind shields.
I really hope XCom gets patched and eventually taps into the huge potential this games multiplayer has. I would hope at a minimum the bugs get fixed and I would love to see some new additions, like more maps and other game modes, like king of the hill, for example (To prevent camping). Also a way for the squad matchups to be less random.
I've been having so much fun, I've been willing to play through the bugs and other things I mentioned. I've notice a lot of other people have been willing to do the same too. Don't get me wrong about this post. You should absolutely play the multiplayer, it is fun and addicting.