I'm fascinated by that "behind the scenes" stuff, and we really enjoyed KttK.
With that said, if you're already questioning the impact on your psyche, I'd avoid the tours. Based upon the concerns posted, I think you know exactly what you'd be getting into. On our tour, we saw things like:
- Normally morose Haunted Mansion CMs yukking it up in the break room.
- The back of Splash Mountain, including the trash reclamation facility right there (and boy did it stink).
- Utilidors - although that was nothing special. It was kinda disturbing to see that the Utilidor maps used rides that have been closed for 10 years as points-of-reference.
- Some spare parts for the Jungle Cruise, including half of a hippo, which is all that really exists under the water.
- A group of about a dozen CMs preparing for a show, 5 or 6 of which were half-dressed characters. This was probably the most un-Disney thing we saw...not only because of the costumes but also the general attitude. These CMs were "off stage" and you could clearly tell that they were just a group of 20-somethings who weren't overjoyed about the prospect of wearing fur in 90+ degree heat. We saw them "on stage" a few minutes later, and they were just as chipper as any other CM you would exepct to meet interacting with guests. But our encounter really drove home the fact that even the CM attitudes represent...manufactured 'magic.'