Our sister site TouchArcade has a walkthrough video of the game that shows off some of the gameplay on iOS.
On touch devices, you control Tommy with virtual buttons and a roving virtual stick. It isn't the best solution in the world, but it works OK. Punch, car jack, and sprint are presented on the right half of the screen. Movement is available on the left. When you jump into a car, the controls change. A two-button directional pad replaces the stick, and car-specific actions like hand brake pop up on the right.
We haven't noticed many notable mobile-specific features. Our gut says that the textures on the buildings in particular have been cleaned up a bit. Also, the frame rate seems a little bit smoother, maybe on par with the PC and Mac versions
Grand Theft Auto: Vice City is available on the App Store for $4.99. [Direct Link]