My fiancée and I did the VIP last August and we're making an impromptu trip out to SoCal again in a couple weeks. We've deiced to do VIP again. You really do see a lot of behind the scene things that you wouldn't otherwise get to explore on the regular studio tour. Our group was about 6-8 people. When boarding the trolley, another group joined in with us. It was nice being able to ask questions and the guides would answer/provide input. We were able to walk around the crash site from War of the Worlds, the Courthouse Square, and Little Europe and also went into the prop rental warehouse. After the studio tour bit, we went back to our smaller group and we rode all of the big rides, front of the line. The guide would explain the ride, and you could opt not to join. He would also hold all of your bags, which was nice. We ended up seeing the special effects show as a group. Somewhere in there we broke for lunch which was a very nice buffet. Once your tour is over (about 6 hours), you're free to go on your own. You still have your unlimited front of the line privileges, but by then you'll have probably ridden all of the good stuff, so you could use your time to hit up shows or re-ride some favorites.
My recommendation is that if you do end up doing it, you may as well get your monies worth and schedule it for as early as you can. The first tour is at 7AM and they want you there at least 20 minutes ahead of time to check-in, and make sure your group is all there. Plus you'll want time to enjoy the breakfast spread. I know 7 AM isn't very appetizing if you're on vacation, but we're early birds, so it works for us.