If you watch this film as "entertainment", this is not a perfect film, but it's pretty good. Acting, lighting etc are all excellent. The continuity just seemed a bit odd in places.
More importantly, as a telling of history, this film is extraordinary. I had never heard of Katyn before buying this DVD and I suspect the same will be true of many others. Speaking with a Polish friend today, I mentioned that I had just watched this film and even now, in barely more than a whisper and with a visible sideways glance as if she was still worried about saying it, she said that until just a few years ago it wasn't a subject that was allowed to be taught in classes. The former Soviet occupation/rule still leaves its mark on people today.
I think it's important that people watch films like this. It's a way of learning history, understanding some of the tensions between different countries, seeing how history tends to repeat itself (Srebrenica - not the same, but similar in many respects), and hopefully from that understanding, stopping these things happening again.
Unusually, the interview with the director after the film is also very interesting. It's not the usual nonsense that you get as an extra on a DVD, this is a documentary in itself.