Silk Route tour

This trip is a fabulous experience. I looked at a lot of companies and chose Eldertreks, a Canadian company which limits their tours to 16 passengers. The person who guides it, Roger Burrows is one of the best guides I've ever encountered. What I like about Eldertreks is that their itineraries are longer than most - in this case, 27 days. Here is the itinerary:
http://www.eldertreks.com/tour/ETTD000424

At first, the cost seems pricey, but everything is included - all meals, tipping to local guides and drivers, all drinking water,etc. The only tip you give is to the main guide. Whatever company you choose, make sure you start getting your visas early. Except for Kyrgyzstan, you need a visa for each country. This is one time when I didn't mind paying a visa service to help expedite things.
The 'Stans have everything, history, culture, scenery. It is a great experience.

I also traveled to the 'Stans with Eldertreks and would recommend it if you meet the minimum age requirements. I have used Bestway for four tours. It was good in Iran; okay (with some issues) in Egypt; very poor in Jordan; and fair in Colombia. Personally speaking, I will not travel with them again.

A very picky friend of mine took the 'Stans trip with Mir, loved it (though pricey) and thought it was one of the best trips she had ever taken.

A friend and I took the Mir Five 'Stans tour in April of this year and found it wonderful. I can't recommend it too highly though, as mentioned earlier, it is not the least expensive way to travel across these five countries of Central Asia. I've not traveled with the other companies mentioned so can't shed any light on their likely performance.

Our group was only 9 (maximum of 16, minimum of 8). The vast majority of the ground travel was in a full-size bus, so there was more than enough room to spread out, get a window seat, etc., and that would even be the case if the group had been 16. We had an excellent leader (Uzbek, fluent in English, Russian, Uzbek, and others) throughout the entire tour, plus local guides except in Bukhara, which was her home town.
Each day, Mir had some extra activity (lectures, performances, fashion shows, etc.) at lunch and/or dinner. We skipped one or two just to have a little free time. Food was good and, if anything, we felt overfed. Hotels ranged from adequate and best-available to excellent and upscale.
I would add that we had a particular interest in archaeology and rock art and had Mir provide a 3-day pre-tour from Almaty and a 3-day post-tour in Ashgabat and Baku. The latter had a free day in Ashgabat, which was a pleasant relief after the structure of the (or any) tour. We could get up and have breakfast when WE wanted! All arrangements for the pre- and post-tours were excellent (though the hotels outside Almaty were basic but the best available) and beyond our expectations.
We flew westbound from San Francisco and spent a week in Japan on the way to Almaty, which eased our time transition. Remember that Central Asia is the other side of the world, so give yourself some time to adjust if possible.

I did not do the five 'stans tour with MIR as I prefer to travel more slowly. However, I did do the Uzbekistan tour this September. My opinion of the tour is somewhat mixed, especially given the very high mark up oper traveling independently.

My summary is here, MIR's response is near the end of the thread:

www.fodors.com/community/asia/the-not-all-golden-road-to-samarkand.cfm

I did the Five Stans tour with MIR last year. It was a GREAT trip. The itinerary, guides, hotels. meals and entertainment were all excellent. I have taken several tours with MIR and have always been impressed with the quality of their tours and the responsiveness of their staff when planning a trip. They are not the cheapest tour operator, but I think they are great value for the money when you factor in everything that goes into a tour.