Just wanted to let you know I had a great one day tour of several Xi'an historical sites with Mr. Bryanbai Chen. I found Bryan on Synotrip (http://www.synotrip.com/bryanbai) and he had numerous glowing reviews from several satisfied clients. You can also find his personal website here: http://www.xianhistorytourguide.com.
I booked Bryan well in advance knowing I would be in Xi'an and need airport transfers to and from the Hilton Xi'an (after hearing horror stories about taxi touts), as well as needing to get to out of the way sights like Hanyangling (Tomb of Emperor Jingdi). Bryan was extremely responsive via email, and after a couple back and forth messages about itinerary, we settled on a price suitable for both of us.
We hit Hanyangling on the way from the airport, then headed to the impressive Shaanxi Provincial Museum and scenic Big Wild Goose Pagoda. From the minute we were in the private van driven by Mr. Li, Bryan had so much useful knowledge to convey about the history of Shaanxi province, Xi'an, and China. Not only was he a wealth of information, Bryan was fun and easygoing, happy to linger for extra photos or move on past another set of artifacts. We even went to a local noodle shop for lunch to experience how real people eat in Xi'an. If I had the funds, I would have also hired Bryan to guide me at the Terracotta Warriors, but I was able to manage to make it there and back on the #306 bus plus read the explanatory signage.
Driver Li was there right on time at 5:15 AM to take me from the Hilton back to XIY Airport. I highly recommend Bryan's services for transfers and a knowledgeable and friendly guide.