The check at the border of Uzbek side actually went very smooth. An officer at the passport control flipped at the pieces of paper of my registration and gave a glance. That was it. He didn't even collect them. I could have camped more times, and didn't have to make fakes. 
There were basically no signboards on roads in Turkmenistan. I had to ask the way in every big junction. Everybody kindly showed me the direction, often voluntary before I asked. Many were friendly. 
The road from Turkmenabad to Mary was wide and good, but it became narrower and bad after that. It always went up & down gradually, and that killed the speed of my bicycle. I wished the altitude meter of my wrist watch hadn't been broken.
The land was mostly a desert. It was cold every day, especially at night. My small thermometer indicated below zero till eleven o'clock in one morning. Daytime was only about nine and a half hours those days.
Satellite TV in cafes on the way could show American TV programs. I saw an internet cafe in Turkmenabad near a market. (I had heard there were only a few only in the capital.) Big tracks from Turkey (Iran as well?) frequently passed by. The country was not closed as I imagined. But anyway, five days were too short to know anything.
The whole distance was a bit less than 500km after all, not 540km, because local people showed me a short cut along a big water reserver near Hanhowuz.
4~8 Dec 2008, Turkmenistan, 10582km-11078km
