We've been on 4 ABD trips--we had not traveled out of the country for a long time and decided as our son was getting older that we should all see the world. Expensive, yes--but we believe in the long run there is no better education. We went with a different tour company to Ireland--the kids did great, but they were the only ones under 18 on the trip. The guide was very kind to our young daughter--and we did quite a bit on our own. We had previously been on the Disney cruises and enjoyed having everything taken care of (the transport from the airport to WDW, then from there to the ship and then to the airport was great). In 2007, the Disney Magic cruised the med so we went all out and booked that and then heard about Adventures--and lo and behold we were able to hook up the Italy trip before the cruise. It was probably too long for the kids to do both--but we absolutely loved Adventures. I had never felt so relaxed--and spoiled--on a trip before.
We we followed that with China in 2008 (in June, pre-Olympics) and were absolutely bowled over by that trip. (So much so that we went and booked the London/Paris trip for xmas 2008--with Christmas in Paris). We liked the holiday trip enough to try it again, this time in Germany in 2009--and again, with the two guides and the local guides, we felt immersed in the culture, and able to go along for a great ride.
We have been somewhat adventurous on our own with each trip--arriving early to take in sites (Rome, Bejing, London, Heidelberg) and get acclamated to the time zone. In Germany we stayed two extra days in Munich and made it to Salzburg--and in Paris we stayed two days extra to take in more of the city and
Disneyland Paris. I'd recommend going early always--we saw a lot of weather issues in Dec 2009 with others in our group, some missed the first couple of days--and as for trips on your own or during free time, the guides supplied us with maps, train schedules, helped us purchase train tickets in advance, wrote out directions in Chinese etc etc
Bejing had challenges for Disney--and for us--especially with changes in the schedule due to the horrific earthquake in the Chengdu region (we didn't go there, but had an extended time in Bejing--Disney arranged for our group to see Pandas at the Bejing zoo, during feeding time so they were up close and very active. We hail from San Diego--and the Pandas in our zoo are frequently not visible or not very active!).
I think the biggest hurdle Disney has to overcome with these trips is the idea that (like the cruise ship) there are characters about, or that the trip is geared for kids. It isn't--the kids get a lot of attention and there are things just for them--but it gives the parents a break too, and the main focus is on the people in the country you are visiting (and the highlights, too--so for example on the Great Wall, you walk it, the Disney group encounters warriors on the wall--and we have lunch at a school house/glass works just below the wall with kid activities thrown in).
I'll let others expound--and would be happy to answer any questions about our experiences. I'd also recommend checking out the trip reports--some are very detailed with photos.