I took the Backstage Magic Tour last August. I enjoyed going behind the scenes, especially at Epcot, where they took us to World Showcase (and American Adventure) before it opened to the public. At Hollywood Studios, they gave us a look at costuming, which was an interesting, and the tour also went behind the scenes at the Tower of Terror. We didn't exactly go into the Animal Kingdom Park. Instead, they showed us where the floats are stored for Mickey's Jammin’ Jungle parade. Finally, at the Magic Kingdom, we took a tour of Main Street and the underground utilidors. Among the park visits was a trip to where the topiaries are grown and to central shops, where rides are repaired and built (this was great). Lunch at the Whispering Canyon Cafe was also good. Is it worth the money? I think it's borderline, but I tend to lean toward yes. I think the tour only makes select stops at certain parks because of, one, time (it’s already a 7 hour+ tour) and, two, because most of the parks have their own tours and they don't want them to be repetitive.
Let me know if you have any other questions.