With expansion packs, online and a certain Hasslehoff, this has become one of the best games available on the PSN today.
It is worth noting that at this point I had recently bought the new pack that allows for Pain darts and Pain Fortress, making me back up to date with all main additions to the game (not counting the characters). The ability to play your own music during the mayhem is a good bonus and is a good step for PS3 against the 360. Originally the game only had one level - Downtown, but the add-ons for it add an additional two levels - Movie Lot and Abusement Park. These are both great fun to play and give plenty of oppotunities for random sillyness. That pretty much sums this game up, random sillyness.
This is even better to play multiplayer and the new Pain Fortress mode is hilarious if a little time consuming. I have only bought one additional character for the game but his name is David Hasslehoff. A great opportunity to throw him into numerous explosive crates (I don't actually hate the Hoff, its just fun.)
To sum up, this game is very simple and worth the additional add-ons. It is frankly hilarious and I hope there are more add-ons for it in the future.