I did a check on the Rotten Tomatoes website to see how the critics like it. I don't take the critical consensus as gospel about a movie's quality. Some of my favourite films are deeply divisive, it seems. At any rate, Iron Sky has received about a 40% rating. It fails.
One interesting thing, though: American critics haven't weighed in yet. If we look at who likes it, I see reviews from the Daily Mirror, The Birmingham Post, Sky Movies, The Mercury, and At the Movies. The first three are English; the last two are Australian. It will be interesting to see what happens when it receives wider distribution. I suspect that it shows the President of the United States to be Sarah Palin would make some American critics cringe and others cry foul. This is enough to explain why...supporting a violation of Godwin's Law is not smart politics.