I saw this at my local film society (its first public showing in Kent, where it was made). I thought it was pretty good by any standards (and not just "pretty good for a film that only cost £520,000").
If you're expecting state of the art special effects and CGI and an extended gore-fest, you'll be disappointed, but it's highly watchable, engaging, sometimes funny and made me jump more than once!
In a Q+A afterwards, the director and the director of photography admitted they had had the same problem that a lot of creature feature makers have - the creature never looks as convincing on screen as you had hoped (we all remember the rubber-looking shark in Jaws!). As a result, their creature is only briefly on screen but its presence and menace are still felt.
All the actors give a good performance but I'd maybe highlight Shaun Dooley as Calhoun, looking like a slightly younger Russell Crowe, and Corey Johnson as Hank.
I'm not a big horror genre fan myself - if you are, you might find yourself insufficiently scared - but Blood Moon still stands as a well-made indie film. It benefits from having been shot in Laredo, a Western town in the UK recreated by a group of re-enactors - the period detail throughout is much more than skin deep and it's a convincing enough location to have fooled many people into believing it was shot State-side.
It's done pretty well on the festival circuit and, as the first British-made Western since "Carry on Cowboy" in 1965 (reputedly), I think it deserves watching.