We hotwired a car to try it out and were presented with a comic book panel-like inset that had us rotate the analog stick, time L and R button presses and rotate the stick again. According to Rockstar, similar mods have been made to all the minigames, but no minigames have been added exclusively for the PSP release. (Developer Rockstar Leeds did, however, deem the need to pay bridge tolls unnecessary.)
We were quickly pointed toward some added elements, specifically a new aiming "arc" for lobbing grenades and Molotovs while driving, copious bloom lighting (it was a rainy night) and punched-up explosions. The in-game "PDA" has also been redesigned slightly to mimic the PSP XMB interface.
Check out freshly captured new screens in the gallery below: