We had a very nice visit organized by Woeser at Road to Tibet, with an excellent and knowledgeable (as well as very nice!) guide, Lhamo, and a very patient driver who had to put up with foreigners not used to steep mountain roads ... Lhamo, our driver and Woeser, all three of them, just know so much about Tibetan culture and also about how visitors acclimate to high altitudes and Tibet in general. Train tickets are very complicated to get and Woeser is the only one who was able to get us some train tickets to travel over to Tibet (and it is highly advisable to go by train to avoid sudden altitude exposure).
It is often unavoidable to stop in Xining (we had to do that too), train tickets are just terribly oversubscribed in China and difficult to get. We flew back to Beijing on China Southern (using ctrip to book the flight tickets), quite satisfactory. I think it is fair to say that Tibet is such a complicated place to visit that it is likely that some mishap will occur, one cannot expect everything to run like clockwork, but the key is good will and knowledge and the folks at Road to Tibet had lots of both to share ... Permits are also not trivial to obtain and there again Woeser is able to manage this ... The hotel we stayed at, the Shambala Palace is extremely well located (it is important to stay in the old town in my opinion) and has a lovely Tibetan atmosphere and decorations as well as a few imperfections ... I would absolutely go again with Woeser if I get a chance to go to Tibet again. Visited June 2013