We have a friend who has recently cycled through Iran (en route from Turkey to Thailand via Iran, China and lots of other countries.
He found the Iranians very hospitable and apart from the police following him for half a day before checking his papers, had a great time and was very impressed. He has been stopping in low cost accommodation if a camp site wasn't available.
If you want to check out his opinions on some of the countries he passed through his blogg address is:
www.roddo.net. The month for Iran was April I believe and up to 23rd July he had cycled 9,267k