We loved the Keys To The Kingdom Tour - it was a fascinating insight into all that goes into running the park and I enjoyed hearing about the history of the park too. I would recommend it for people who are really interested in this. We went on two rides as part of the tour - Jungle Cruise and the Haunted Mansion.
This tour is NOT for the faint-hearted - you do spend a lot of time walking and standing with just the break for lunch - about 4 and a half hours in duration, and it can get pretty hot too so do have water with you. That said, in the small garden where you register next to City Hall, they do have a fridge under the table and will give you a small bottle (no charge). .. we had to ask for this, it wasn't volunteered!
You cannot take cameras on the tour - they took bags and cameras and put them in holding lockers in City Hall whilst you toured. (You are allowed small bags or bum bags).