The new game on PSN for 9 bucks is well worth it. I downloaded this game not too long ago with my share group and have been playing it quiet a bit lately. Its by far the best game on PSN I have seen yet and it is extremely impressive. The physics are rather cool and the graphics are amazing, especially for a 300mb game. Another plus in my book is its hard as hell. I have probably put in 3 or so hours of play and only gotten to the boss of the first world once at which point I got my *** kicked.
The game takes some getting used to but its a great time and I suggest it for anyone who is looking for a game that is pretty quick to pick up but will take a while to get good at and has a pretty cool co-op mode.