It's more than a fancy line cutting service. Our guide definitely talked to us about the history of
Disneyland. We also talked a lot about his experiences, both as a VIP guide, as a CM in general. He told us some things about the park and some of the attractions that we didn't know about. We talked about things like the basketball court in the Matterhorn, the fact that it's warmer in parts of Alice because it's above the hell scene in Toad, etc. We talked about what some of the other tours were like, etc. I don't recall what else, but he was very friendly and very informative. He didn't just randomly start talking to us about these things; we asked.
Depending on the size of your group, it may be difficult for the CM to talk to you while you're going from ride to ride. But you do spend some time in line, which is a great time to talk to them.
One of our favorite parts of have the guide was the ride photos. They are able to go on some rides with you (not anything they'd get wet on). The pictures of our guide on the rides were HILARIOUS. He made the best faces ever. He also helped us out getting some great photos on our own. They know all the best places.
My kids were middle school and high school age when we did this, and it is by far one of their favorite memories of Disneyland. Not because they got to go on so many rides, but because of their experience with the CM.
One thing I'd recommend is that you ask to ride in the wheelhouse of the Mark Twain if your group isn't too big. Yes, you can sometimes do this on your own, but I think it helps to have the CM request it.
Another benefit is that if you don't do the VIP first thing in the morning, you have the morning to do whatever you want. Normally we rope drop and spend the first couple hours in the park doing everything we possibly can. But because our tour didn't start until 10 (we planned it that way on purpose), we had the first few hours in the park when it was less busy to just enjoy the park. We did Peter Pan, then just had a relaxing breakfast at Carnation Cafe. It was great just relaxing and watching a morning at Disneyland unfold without being rushed.
You may already know this, but most people do tip the guides. They'll also hold a table for you if you while you're in line if you want to stop and eat. They may or may not eat with you. Also, be prepared to be very tired by the end of your tour. I never realized how much rest you get by standing in line.
Hope you have a great time!