The Shah was "no boyscout", but he was trying to modernize Iran. He ruled with an iron hand, but how else can you deal with the radical Muslim elements, like the Ayatolla. The Shah was too kind, he should have executed the Ayatollah, instead of merely exiling him.
The Shah, as part of his "White Revolution" allowed women to vote, hold jobs, in general tried to secularize the country and bring it into the 20th century.
The Ayatollahs, took it back to the stone age, as the Taliban has done in Afghanistan.
The Shah was also a very reliable friend to the US and the West in general.
I have no truck with tyrants. When you say "he ruled with an iron hand". That's wrong. Maybe that is why the Persians have lost their way.
I worked with some Iranian engineers shortly after the Iranian Revolution. Through family contacts in Iran, their assessment of Iran was that the problems under the Shah were nothing compared to the mess made by the mullahs. I asked if it was going from "bad to worse", the reply was "No, things have gone from very mildly bad (under the Shah) to impossible (under the Ayatollah). Things have gotten so bad people would even welcome the Russians."
IMO, I don't want to see a war in Iran (but realistically I would also say "keep your powder dry"). This is the best opportunity to help change the regime since the Solidarity union in Poland.
You're right about the Shah. The paradox is that it seems the Shah shouldn't have bothered to modernize Iran. Look what he got for his efforts.