Politically, I did not think that the movie was such a big deal: people who dislike Bush will agree with the movie and people who love Bush will think that the movie is unfair.
However, I must say: Michael Moore is a very, very skillfull film maker. I recommend the movie for both people who dislike Bush and for strong supporters of Bush: interesting intellectually, for sure!
I think that the quality of this move is so good that it sets new standards. Anyway, do not go see this movie for political reasons - go see it because it is a well done film. I think that this movie is now part of our culture; for my Republican friends: do not miss out on seeing this movie just because it tries to make Bush look bad.
BTW, profits for the movie go to charity (deal between Disney and the Weinstein brothers to get the movie distributed).