Bottom line is you always have to go into movies like these with an open mind, because you never know what you are (or are not, for the most part) being shown. Things get left out, words get twisted, but the general idea remains the same. Bush is responsible for many of the negatives presented in this film, yes, but you have to understand that any movie will always be somewhat biased, like it or not.
The movie is a bit of propaganda against him, but it also does hit on some key factors that show some problems with Bush in office, and U.S. politics in general.