The UPH will get you into Disney Quest. Most of the games are free. The exception are games that award tickets to be redeemed for prizes. We didn't play these games, so I don't know the cost.
The games included in admission were plenty to keep us busy (i never even saw the area with the extra charge games). There are regular arcade-style games (fun to play without having to insert quarters!), but the main attractions are the virtual-reality games. Pirates of The Carribean is amazing! It's more an interactive ride than video game. There are also several attractions in the Create Zone area that allow you to get creative with animation, designing a roller coatser, and other stuff.
With a UPH, I would recommend at least stopping by (since it's included in the pass, anyway) if you have time to spend outside of the theme parks.