DH and I did this tour just on 7/11. Our tour guide was Robert and even with 13 people on the tour this was fantastic. We have done 5 backstage tours and this rivals Keys to the Kingdom with Rae as our guide. (DH will still tell you his favorite is the Segway Tour!) We learned information about everything from the tiles used in constructing SE, visited lounges in SE, Living Seas, areas no longer used in Imagination, learned about traffic flow in Land, saw fireworks barges, learned about Test Track, saw the "real" side of control in M:S, visited costuming, etc.
Gee, can you tell I liked this tour? We also got special Illuminations viewing in Italy the evening of our tour--great location.
Remember tour discounts with AP,, DVC, or Disney Visa, and I'd request Robert as a guide.
The only down side was tour length -- 5 hours, and we did get a break at Seasons in the Land--just enough time for a snack (needed at that point).