I went back to play some again. They've released 4 free (yes, free) DLC's and they are all pretty great. The maps are good, the new weapons are fun, and the new Enemies (The Collectors and a few new baddies for the other Enemies) are a nice touch. The added a ton of new playable characters.

I'd say that ME3 multiplayer was one of my biggest pleasant surprises of the year. I gagged when I heard ME3 was doing a MP game and I'm amazed at the time and care that went into it. And moreover, I'm impressed by the level of support for the MP. There are just so many options between biotic powers, weapons, and equipment. Great great stuff.