I have to say I am rather ignorant of Iranian politics. I had good friends from Iran when I worked at the Kansas Geological Survey during my grad student days. I tried to avoid political discussions with them. It seems to me they were in the US, in part, to avoid the "unpleasantness" associated with the overthrow of the Shah. I'm not even sure I know if they supported the Shah or not. Today, I remain somewhat ignorant, but a bit more educated and dramatically more cynical.
It is amazing to see the pictures of the protests in Iran and to follow the tweets from Iran. How good it is to see so many people passionate about democracy in any country that they risk their lives to protest. How insane of the power structure in Iran to believe that no one would question the highly suspicious vote counts produced almost immediately and released equally quickly! It is crazy to think the vote came in that quickly and that support for Ahmadinejad was so lopsided. I have heard reliable reports that no candidate other than Ahmadinejad won his own hometown and then I see the crowds and I have to question the reported election results. The results were so poorly constructed, even the "Supreme Leader" had to backpedal a bit and ask for an investigation. Of course, the investigation will be conducted by the same men who conducted the election, so a great deal of backpedaling will be necessary for there to be any change in the end result.
I find my reactions ranging from amazement at the arrogance of the power structure to cynicism about just how much change Mousavi would produce if he were elected. After all, his history is quite conservative and he has had his turn in the power structure in the past. Sometimes I look at the pictures and remember Tiananmen Square protests. At the time, we really thought those protests would force change in China, but the change, if any, was very minor and very slow to appear. One can hardly expect the Iranian protests to be much more successful.
Without regard for the long term prospects, my final reaction is support for democracy and for the thousands of protesters in those pictures and on Twitter.