I played this over the weekend on my friend's system, and I must say that it's excellent.
I thought it'd be a simple, childish "walk-through" game with little challenge or excitement, but boy was I wrong. The environments, objects and enemies are so dynamic and fun to play with.
What I really love about the game is that object behaviour isn't scripted; it's pretty much all left upto the physics engine, and when there are explosives and jetpacks and 4 players involved, much hilarity ensues.
I haven't even tried the online user created levels yet because the story mode has kept me very well engaged, but I look forward to seeing the best of the community creations.
Definitely recommended.