I've been playing the Uncharted 2 multi-player demo since I pre-ordered the game last week, and it is truly impressive. I'm not very good, but it's a blast. I was able to score twice at Plunder to secure my team's victory. Great feeling there. A tutorial would have been nice, but I'm slowly catching on. The public demo may go up in the store this week or next.
I don't have many other multi-player games AE. I haven't tried any of the co-ops in Resident Evil 5 if you own it. Or there's always Little Big Planet. I'm CreatureCantina if you want to add me.