I have been on 2 "high end trips" with Trek Travel and a slightly less plush trip with Classic Adventures (they work with Bicycle Adventures). Everything was great on these trips; the guides, especially at Trek were unbelievably knowledgeable and great leaders. I know several people who have done Backroads trips and I haven't heard any complaints.
The only negative thing I can say about these trips is that some of the other participants were a bit obnoxious, at least to me. When I get back from a hard day of riding I do not want to sit around in sweaty bike clothes and drink beer. I also can't stay up until midnight getting drunk if I have to be up at 8 getting ready to ride again. On the trip we did to the Czech Republic and Austria, half of the group were friends and had known each other since college. They weren't "bad" people, but it definitely made the trip seem like there were 2 groups. The Classic Adventures trip we did to Quebec last summer went much better, even though the level of support was a teeny bit less (2 guides instead of 3). We purposely chose a trip that was listed as easy/moderate so there would be none of the competition we saw on the other trips. Most of the people were strong riders, just older like me.