I had high hopes for this film, as did many it seems. The first thing to immediately hit you will be the rather bland CGI used, it's way below standards for something so recent. When you look at some of the animations in the 40k video games like the intros to Dawn of War II for example, this falls flat on it's arse.
As far as the story goes, it's not terrible, there's some brilliant use of tension and atmosphere but it's just a little stark, the story feels a little small in scale for such an epic brand. The battle sequences are well animated, and violent, but it's nothing particularly special.
I think it's been a fairly pointless endeavour for Games Workshop on the whole. It wasn't received very well and could mean no more movies are made, which would be a shame because there's so much potential just waiting to be used. I would recommend watching it at least once for fans, but don't expect to be blown away or gripped by a dark, engaging story.