From one Jeff to another:
Last September my wife and I took the 18 day Collette China and Tibet tour with Marriott Vacation Club Points. The tour was with Collette Explorations, which is Collette's small group division (I think that we had 16 people in the group); it may not reflect the experience in the other Collette division, which seems to offer shorter tours with larger groups.
Our tour was excellent and our tour manager was extraordinary. He was extremely knowledgeable and gave us insights into China that went well beyond anything that I expected -- and I had high expectations. He accompanied us for the entire 18 days, serving as our guide in Beijing, and adding his expertise everywhere else. I might add that I am a vegetarian and the tour manager made arrangements everywhere that we ate as a group so that I could enjoy balanced and interesting meals.
We also had a better experience with Collette than many report, but I think we had the same guide as jeff76543 - We were in France (Paris, Normandy, Provence, Nice and Monaco), and the guide talked very enthusiastically about having given their China tours for years.
I'd rate Collette middle of the road, probably standard for the price point. We had 50 people, mostly teachers, one other family MVCI-related. The guide was very personable, enthusiastic and experienced, EXCELLENT at handling food/personal/arrangement/group dynamics issues, and reasonably knowledgeable about the major targets of the tour. He was NOT university-level sophisticated about art or religious sites. (Thanks to a 3G Kindle at hand on the bus/train, and a Guide Bleu, I was able to fill in a lot.) Overall, we had a fabulous trip, but we did our own research (for sites and for restaurants), used our free time well, and even left the group for several hours on occasion (with guide's assent) when we wanted to see something other than what he was showing the group. (I definitely couldn't do that in China!)
However, I don't plan to use Collette again, at least not for a standard 50-person group. I suspect it is standard for the price level, a level that some owners would purchase on their own, but it would be nice if DC would also partner with a higher-level operator, for those willing to spend the extra points.