Not sure if you guys have played the ME games, but I enjoyed them immensely and am pretty excited for Mass Effect 3.
The demo is out now and it's pretty fun. The MP is basically horde mode, or spec ops survival if you want to use CoD as a basis of comparison. It's done really well, you play 10 waves and level up each class and earn money that you can use to buy packs which unlock weapons and characters and stuff to use in the game. It's good times and has a lot of carrots at the end of a stick to keep you going.
Let me know if you guys want to jump on xbl and play it.