The movie's received very mixed reviews, but personally I liked it quite a bit.
It does have some problems with the writing and pacing, but overall it is very enjoyable.
I don't know if you are aware of the history of the production, but basically the director and VFX guy are known amongst Star Trek and Babylon 5 geeks for their long running Star Wreck series they did in Finland, first it started as short animations, leading up to a feature length film made on a $10,000 or so budget, 90% of it filmed in one of their mom's basement, and most of the CGI done by Samuli Torssonen, the guy who started the whole thing.
They released the movie on the internet for free, and they've actually sold it to numerous countries since.
This was in 2005. After that they started working on Iron Sky, they basically worked their asses off since then, producing teasers and trailers to entice investors.
In the end they managed to raise almost a million bucks in donations and investments from fans of their Star Wreck movies.
At the end they made it with Finnish, German and Australian money, making it an international co-production.
The entire budget was under $10 million I believe.
Also what's amazing is the CGI, which is on par with most big budget Hollywood productions IMO, was done in only 9 months by a team of 20 or so.
My hat's off to them, an incredible feat.