My experience with Travel Gobi Mongolia (TGM).
A few months ago, I had inquired about a trip for June 2013. I received a very prompt response from Ganzo. He was willing to customize the itinerary to fit with my schedule (late arrival and switching sightseeing order in Ulaanbaatar) and made helpful suggestions (hotel recommendation for an extra day in Ulaanbaatar). In addition, I like TGM's option to post my tour on their dedicated "Join-in and Build a group" website so I could reduce my tour price. Unfortunately, due to a flight problem I did not end up going to Mongolia. My deposit was refunded.