UPDATE: I just finished watching the movie. Parts of it are an indubitably sound reminder of the dangers posed by extremist Islam, and the support that it finds from some traditional Islamic religious teachings.
Other parts assert that extremist Islam is a problem at the heart of the Islamic world generally, and of Islam in the Netherlands and in Europe, and not just a tangential matter (the way that fundamentalist Mormon outliers are tangential to modern Mormonism, or, even more extremely, the way the Branch Davidians were tangential to the Seventh-Day Adventists from whom they sprang). But here too Wilders' view seems sound: Unfortunately, while by all accounts most Muslims do not adhere to the extremists' views, the extremist movement is prominent enough in Middle Eastern and European Islam that it is indeed a peril to freedom.
Nor does the rhetoric strike me as excessive. This is of course a rhetorical work, not an academic inquiry, and it's trying to stir people emotionally. But I didn't see much of hyperbole or gratuitious insults. Wilders is arguing against an important and dangerous ideological movement; my sense is that his approach is well within bounds of legitimate criticism.
So I think this is a significant contribution to the ideological debate, and it seems to me that we -- and especially Wilders' fellow Dutch, to whom he is speaking most specifically -- should take it seriously, naturally together with whatever responses might come out.