I probably could have used a gentle easing into the game, it definitely felt like being dropped into the deep end and I'm not super fast on the draw anyways...
I love the art, you've done a good job bringing the scene together and you really nailed the retro vibe in a good, authentic way.
I had a little trouble discerning between the sheriffs and bandits. Do the sheriffs shoot the player?
It feels also like a little juice would really spice things up. Shake the screen a little when I get hit, maybe have cash and other goodies fling out of the bandits on a head shot.
All in all, it was fun once I got the hang of it and the art is very enjoyable. Great entry!