Transport in Iran

Generally there are three ways of transport between cities- bus, train and plane. We have chosen bus and train, and both were fine.
Transport is generally cheap (they've got a petrol, right? :)). From what we heard, a plane is about 40USD. For both train and bus we paid not more than 5 USD. At first I was more favorable to the train , since I saw how Iranians drive, but now I'd rather recommend a bus.

The train.
The train was just fine. We've chosen "the first class" , which was a simple carriage with couchettes. Not sure if the air conditioning was there, it wasn't unbearably hot, but not cool either. It was possible to sleep there anyway (I slept like a child. But don't forget to drink a lot, I woke up completely dehydrated).
It is also a great opportunity to talk to Iranians, they are so talkative and communicative.
Also, there's a restaurant compartment and water in every compartment.
Oh, and Persian restrooms of course. Not in the best condition. Not at all .
Ah, and the strange thing about the tickets. You can't buy them on the train station , you must go to a travel agency. But it's not far at least :)

The bus
Take the "VIP" buses. They're air-conditionned, with really confortable seats, which you can set in horizontal position. Literally! Also you'll be able to get some snacks and cold water all the time. We had one stop, in the middle of the desert, next to Qom. Really scruffy place, don't eat anything there. :)