I've submitted a free update for the Emerald Run game to the app store. The focus of the update is optimization and bug fixes.
As a side note, the game runs marvously well on an iPhone 4S with all settings turned on max. Also, the shadow sample rate is double on the 4S!
On the flip side, there will be speed ups in graphics especially with shadows turned off -- 3rd and 4th generation iPods and iPhone 3GS should see this improvement the most.