My brother in-law and I had a marathon session (8:00PM until 4:00AM) playing Lego Star Wars II Saturday night. The two player co-op is excellent. It's not split screen, you share the whole screen (like Hunter the Reckoning) but the camera angles work much better in Lego Star Wars II. We did not seem to get stuck or dragged along by each other very often. My wife even enjoyed playing and watching this game with us. Definitely a high WAF factor.
At one point we did run into a little glitch. During "Return Of The Jedi" after the Speedster chase, we had to make our way up a large platform in the forest, and catapult one of our characters onto an AT-AT. At this point my brother fell off the platform and he did not die like he should have. He was trapped on the ground below the platform and could not get back up. We tried killing him with the AT-AT so he would re-spawn on the platform, but could not figure out a way to kill him, witch is very odd because I am usually very good at killing my co-op partners

We ended up having to restart the level.