I am also interested in hearing others experience on the tours. I am going to WDW over spring break and am planning on doing a VIP tour. I was planning to do the Magic Kindgom tour but want to hear opinions on all the parks tours.
We did the KEYS TOTHE KINGDOM TOUR at MK in September 08 and I would highly recommend it. The tour was around $60 (I think!) per person, and includes lunch. The tour last 4-5 hours and is a walking tour. You go around every land and go onto 3 rides or so, with the tour guide talking about the secret things and behind the scenes knowledge on the rides.
The tour guide has a mic and we all had a small pack with an ear piece, so you can always hear your guide -they are great as when yuor guide is talking about hings ie. the windows on main street, you don't have to all stop to listen - so you can cover more! You also go backstage behind the rides, and see the parade floats and find out just how small (and normal looking) backstage is - no disney pixie dust sprinkled back there!! You also get to go into the Utilidor - which was the reason 50% of the people in our tour group actually went on the tour- but thats kept til the end!
Overall it was brilliant, and although I knew alot of what she was telling me, I learned a lot too! All in all, well worth it!
I believe SummerinFl has a trip report on it, with a lot more detail in it!