I took it in February and loved it. We started at Epcot, went behind the scenes almost immediately and boarded a bus. It took us around the backstage area of Epcot to the American Adventure, where we got to go backstage and see the audio-animatronics being prepped for the day (very cool!). Then it was on to the cast area at Epcot, where the lockers are and costume check-out are. We spent a bit of time here talking about Disney standards and what being a cast member is like. Then it was on to MGM, where we got to see the costume sewing (for things like princess costumes and special garments) area, which was awesome. We had lunch at Mama Melrose, which was big portions of many dishes for everyone to share- TONS of food. Then we headed to the Magic Kingdom area and went back behind the park to see the Disney Florist (who was prepping for Valentines Day... tons of roses everywhere!!) and the central shops (where they build everything). We got to see ride vehicles being prepped, the paint area, animatronics up close, and all sorts of cool stuff. We went to the Christmas building where they prep the decorations year round for all the parks and resorts. Finally we went to the MK and into the utildors (much better than KTTK for time and what you see down there). Then we drove back to Epcot and were let off outside the park and given a Backstage Magic pin.
My understanding is that the tour may vary from time to time depending on who is leading it (we had a guy who doesn't normally do tours... he was a Disney INstitute guy who normally does speaking enagements... but he definitely knew his stuff and did a good job). Some people have said they've visited other areas, i.e. parade floats at MK, or the laundry facilities. I think it also depends on what's going on and how much time you spend at each place, as they may not have enough time to do everything if something holds you up somewhere. the walking isn't that much- you take the bus from place to place, it's mostly time spent standing that wears on you (I work in retail, so I'm used to it, but I could tell others were getting antsy/sore from standing at times). If you have any problems with stairs or such, there was pretty much always an elevator available, but there wasn't that much anyway.
I'd gladly take the tour again, although I want to do a couple others before i do any repeats (hoping to do Undiscovered Future World and Steam Trains on my upcoming Oct. trip). I'd highly encourage you to take this tour if you're interested in the "workings" of the parks!