I watched Fahrenheit 9/11, and I wasn't particularly impressed, since it didn't cover much new ground.
It's propaganda, and it has strong anti-capitalist, populist themes.
The last part, which covers the war on Iraq is probably the most effective. The visit to the White House of the grieving mother who lost her son in Iraq was gut-wrenching.
Ironically, despite the film's attack on the PATRIOT act, the movie's very existence indicates that the culture of dissent is alive and well in America. I got a fairly good impression of the American system, and it was reassuring to see that some of America's flag-waving patriots are quite unlike the cretins who inhabit parts of the internet.