I've had a great experience with one company, a mixed one with another, and a bad experience with a third. Here's what I encountered:
The bad experience: Of the three tour companies I've used, the worst (by far) was REI Adventures to the Loire Valley. Yes, their trip was the cheapest. But I would gladly have paid more to get bicycles that actually worked, food that was edible, and guides who were more forthcoming with information about the area.
The mixed experience: I've taken two trips with VBT -- one good and one on which we had some problems. The good one was to Vermont; the problematic one was to England, a trip they no longer offer. The problem we had was with one of the guides, who was so obnoxious that the tour members actually fled from him if he walked in their direction. He also seemed to be trying to hit us up for larger tips by telling us how little money he makes on these tours. Totally inappropriate. But I have to say, the bikes were satisfactory, the food was good, and the lodging was competent. Unfortunately, VBT has become a company that now caters to cycling tourists who want to spend a lot of days off the bike. Pay for an 8-day vacation with them, and you'll discover that two of those days are "travel" days, and that of the remaining 6 days, you only get about 3 full days of cycling. When I plunk my money down for a cycling trip, I do so because I want to see the region by bicycle. Since VBT is no longer a serious bicycle touring company, they don't get my business any more.
The best experience: After asking several members of my bike club about their preferences of touring companies, the overwhelming consensus was that Experience Plus delivers the most bang for the buck. So I gave them a try last summer on a trip to Ireland. The result? No company I've used has come close to Experience Plus for their attention to detail. First, they mark the roads with chalk so that the cyclists don't have to keep referring to a map. You have no idea how nice it is to not have to worry if you've missed a street sign in a foreign country. Next, the food and lodging were terrific. I don't eat beef or pork, but everywhere we went, there were always culinary options that were appropriate for me. Next, the bicycles were the best I've ever used on a bike tour. They were maintained every night and tuned perfectly for the next day's ride. And finally, the guides were simply the best I've experienced. From what I've seen on past tours, guides are generally a necessary evil. But they were such a positive and important part of this Ireland trip that the tour would have been greatly diminished without any one of the three of them there. They were terrific tour leaders, wonderful cycling partners, and just great fun to be around. Experience Plus isn't the cheapest company or the most expensive. But I can't imagine a company that delivers more value for the dollar. They have a web site at ExperiencePlus.com
Hope this helps.