I really enjoyed this movie! Here is a review I did at the time on Amazon (though 50% of my four 4 votes said it was unhelpfull!)
I am unfamiliar with the comic that this movie is based on but I am familiar with the `Cowboy and Indian' films that influenced it. Essentially they were popcorn movies designed to entertain with fast paced action and I am very pleased to say that this Sci-Fi take on the genre is a heap of fun as well.
Daniel Craig and Harrison Ford are great as the gruff and tough Westerners and the supporting task is fine too as assorted parsons, bartenders, sheriffs, outlaws and Apaches. It is refreshingly focused on the action, with the romantic elements very much played down. I enjoyed the fist-fights and the great scenery. The aliens are suitably villainous (you can tell they're bad even though they don't have black hats - or any other clothes for that matter), though they did appear a bit too super-powered for the standard Western weapons to deal with. Things are evened up of course with Craig's mysterious bracelet. He uses it liberally too. Indeed, no one really holds back and the climax is quite the kill-fest.
The film also has some blokey chuckles and some eye-candy in the lead actress. There are a couple of nice emotional touches at the end but the highlight for me was the full-blooded tone that was taken with the action. I was thoroughly entertained and if you go into the film, as a previous generation did to watch those earlier `Cowboys and Indians' actioners, you should have a great time too!