I did this trip in May 2004 and it was spectacular. My companion and I bought a package (through a Beijing agent) with car and driver from Chengdu, ending in Kunming. Be sure to take the altitude rise as gradually as you can. I stayed two days Rocky Mountain Park (US) as preparation and took Diamox. We stayed at Kanding, Xinduqiao, Litang, Yading village (Riwa?), Zhongdian, Lijiang, Dali. A lot depends on the weather, and in May we had snowstorms (both at 5900 m south of Litang and at Yading), so four-wheel drive is essential and probably universal. Our driver was outstanding in the difficult weather/terrain, but that's the luck of the draw. Spread the trip as long as possible, as weather and clouds can be an issue. I hear the autumn is beautiful. Accomodations can be basic, but that's part of the atmosphere. At high altitude you're never interested in eating, but the food tastes great when you get "down" to Zhongdian at 3300m!