I believe Red Rock Resort was the first in Las Vegas to have server-based slot machines.

The random number generator is still used. Must be a true random draw each time. What can be changed is the specific games associated with a particular machine. I'm sure you know that you can't tell the payback percent for a slot machine by looking at the machine itself. I'm not sure these changes can be made while a player is playing and has his card inserted; I suspect not.

It does mean that if you're a video poker player, check the machine pay table (visible on the glass) before you begin to play. It many not offer the same game you played at that machine a couple of hours ago.