I did a self supported (short) tour this summer in Europe. When I was figuring out the route, I called some tour companies there. They were actually snobby to me and said no one would want to do the mileage I proposed. They told me I was nuts for planning it the way I was. I was SUPER happy with the mileage. I rode alone so didn't have much else to do but ride, and the distances I did (40-60mi/day) were fine for a whole day. Based on this experience (okay, and n of about 3), I think maybe the tour companies often plan for people who aren't used to riding serious miles. If you can put that aside, any tour with a bicycle has to be way better than a bus!