My wife and I did that for our Anniversary a year and a half ago, and we really enjoyed it. I especially loved the little trivia revealed throughout.
You get a sack lunch at the end, and a great tour around the park, seeing most of the rides and attractions Walt had something to do with (Pirates, Enchanted Tiki Room, Jungle Cruise, and a lot more). I also liked hearing about attractions that closed, like the House of the Future. A special highlight was seeing the lobby of Club 33.
We lucked out since we had a small group anyhow of 6 people, and the party of 4 with my wife and myself were an off duty Tour Guide and her family, so we got double the information, since both guides coudn't help but point stuff out.
"Oh, no no no. What I just got is that you're like a total jacked up freaky-deaky crazy pants!!"
-Dr. Venture, The Venture Brothers