Woeser organized our recent trip to Tibet 29/07/2013-05/08/2013, and I recommend him and his Road to Tibet Travel Service highly to anyone embarking on a similar adventure. First he communicated very well by email helping us obtain the indispensable government permits and customize our ambitious Lhasa/EBC Kathmandu vacation plan. Second, he was flexible in making adjustments as needed (more below) and provided us a very good value for our money. We enjoyed a very special trip to a place that is still authentic and exotic.
We traveled from Shanghai, where we are expatriated, with 4 teenagers. We were met at the airport by our cheerful and very knowledgeable guide, Jin Mei Lang Jie (or "Jimmy" for short) and our driver. At Lhasa's elevation (about 3,000 meters, I think) coming from basically sea level at Shanghai, we had a few problems with altitude sickness, some headaches and nausea. We really enjoyed Lhasa, the people are very friendly to foreigners and unlike the big Asian cities, it is still a place where people commonly wear traditional clothing. And the shop keepers aren't aggressive in contrast to other touristy locations in China.
At 5,000m, during the trip to lake Namtso, we were made really uncomfortable by the altitude. All six of us felt it and we had difficulty to sleep even with some canned oxygen. Even though we are in pretty good shape, just climbing a set of stairs would make us breathless. So, we made a hard choice and decided to cut our vacation short and return home early. Woeser gave us a very fair refund on the unused portion of our trip. I don't think so many other tour operators would have been so understanding and cooperative. That is why I highly recommend Road to Tibet. Maybe you will be wise and take your time to ascend to altitude gradually or maybe simply won't be as affected as we were, but if you go with Woeser, you can be sure he will treat you fairly regardless of the outcome - and that is a great peace of mind to help you enjoy your trip.