As with most tours, the guide can make it or break it.
I took the Yuletide Fantasy tour a few years ago...(December of 2000, I think) and while it was okay, I wasn't thrilled with it. I've also taken the Keys to the Kingdom and Undiscovered Future World tours and preferred both of these. But again, a lot of that had to do with the guide. The guide I had for Yuletide Fantasy was normally a bus driver and just wasn't really on top of the information. To me, that negatively impacted the flow and "magic" of the tour. Plus they used a van to transport us - I think it was a 12 passenger van and there was a total of 12 of us - which was really awkward to get into and out of.
I know others have taken the tour with other guides and really loved it though.