We were on an adults only tour that had 17 people on it. We made steadfast friends right away, and had a great time. Four other couples had already been on other ABD tours, and three of us couples have already booked to travel together next year.
I think the German trip lends itself to Disney a little more than others because of the obvious association that the Romantic Road and the Brothers Grimm fairytales has with so many Disney characters and stories. That said, I didn't feel that it was over done, and the castles were wonderful. I didn't feel as though we had too many castles at all. The balance between different cities and activities (bicycling and archery were both very fun!) made for a very nice trip.
I can send you a link to my photos if you want to share your e-mail address.