I've had varying experiences with different companies. I loved the leaders and food from Trek Travel, but not so much the people on the trips. We did 2 trips with Classic Adventures; the first was great and the second was horrible. The trip was rainy and we got lot of flats. The owners, (well the wife), drove the support van right past my friend who was by the side of the road, struggling with her tire.
My favorite so far is Cycling Country, which is based in Alhama, Spain and they do trips in Spain, Potugal, and the UK. The owners are from London and Canada, gave up the corporate life to start the company. The trips don't have a lot of people, and draw an international crowd. It felt warm and personal. We even got to meet their 3 year old daughter when we rode to Alhama. We are going to do a trip with them next fall (Lisbon to the Spanish border).
DH and I typically don't ride with a group on these tours, but in Spain we did some of the time. The first Trek Travel tour we did was justa weekend in VT., so we could drive there and "test" them out. Half the participants were from the Midwest, and were unprepared for the cold weather in October. They made fun of our winter gear at first, but when it was 38 in the morning and misty, they shut up. They also tried to start political conversations about controversial subjects (i.e. pro-life). On our other trip with Trek in the Czech Republic, half of the 20 people were friends from college from 25 years ago. All they did was drink. The rest of the people were racer types. I had not been riding that long then and I was not happy. But the history, restaurants, and knowledge of the leaders sort of cancelled that out.