I did it several years ago. While I liked a few parts of the tour (like the costume area), unfortunately I thought many parts weren't very interesting. I really, really WANTED like it, but didn't. For example, the Hollywood Studios part of the tour consisted of looking at a "sample" car of ToT, which was sitting in a parking lot behind the building,and having them explain a little about its design for about five minutes. Of all of the things to see at DHS, this is what they picked? A ride car in a parking lot? At Epcot, we went backstage in the American Pavilion show. There were too many of us for such a small space, plus it was really dark, and those of standing in the back couldn't see what the tour guides were talking about (how the show worked "backstage"). Several of us gave up trying to see anything and just walked outside.
I'm not sure what I was expecting, but the tour just didn't seem very dynamic to me. It wasn't worth the money to me (at the time, about $200), and took up almost a whole day. I was disappointed.
In contrast, I absolutely loved the Keys to the Kingdom tour at MK and what used to be called the Backstage Safari tour at AK. Both of these tours were fascinating to me. So I definitely like/love WDW tours, but not Backstage Magic.