This version of the game includes brand new moves, new enemies and stages, hidden unlockables and achievements, and a the ability to team up with a friend via Bluetooth and tear through the mean streets in a co-op mode. Also new to the iPhone version is the ability to play as characters other than original heroes Billy and Jimmy. Players can now battle through the game as any character, including enemies, bosses, and hidden characters.
You can read about the rest of the features on the official App Store page. The game is currently priced at $3.99 but will increase to $7.99 in the future. So if you are on the fence about making a purchase, you might want to decide sooner rather than later.