All reports suggest a massive turn-out in Iran, itself an indication of democracy's potential there. The Guardian has a live updated stream of news. Here's a first hand account from one of their readers:
Today temperature in Tehran rise to 90 F (32'C), warmer than all days before, and yet people were and are standing long lines in shade and under blazing sun. It is an odd image of Tehran: quiet streets, deserted shopping centers and yet crowded mosques, high schools, schools and colleges. It is election day.
The stations were and are packed with lines coming out of the building and going around the corner. The individuals waiting in them are from all walks of life, there are Chador wearing women, young ladies wearing the latest fashion and make up, there are old people walking with cane and there are young students with their notes and textbooks in their hands, it is a long wait. One voted told me he and his sister waited for 2 hours and half to cast their votes. There is an air of a united people present that makes one feel romantic.
I voted in Al-Zahra University station in Vanak Village, it took me 45 minutes waiting time. Most people around me were voting for Mr. Mousavi. With number present today, one wonders if this is going to be a landslide.
We should be wary. The regime has stuffed ballots in the past, and many of Ahmadinejad's supporters are unlikely to be emailing the Guardian. And yet one senses something in the air ... something that could make Elliott Abrams panic.