You pay an entrance fee of about $10 or so and then it is unlimited play. YEAH!
There are 130 machines -- new, old, and in between. My favorite pinball game was probably The Hulk. I was even able to play a Pac-Man game that mixed pinball and the original joystick game on a screen.
We stayed and played for about an hour and then decided to go. It was a lot of fun and definitely worth the entrance price - but also quite noisy with so many machines going at once!