Okay, I'm only in the first mission or so of Call of Juarez Gunslinger, but I am REALLY enjoying it. Happiest I've been about a $15 game purchase in a while. Basic user interface stuff like the mouse wheel works, the menus are responsive, and the game seems to run great on max settings on my old e8400 + 5850.
I think I saw someone mention that there is not an option to change FOV, and I don't know if there is even a config file way to change it. I don't think it's bothered me so far.
The graphics actually look quite nice to me, though I noticed one low budget touch already, people don't move their mouths when they talk. The voiceover work is good, the music is awesome (I think I even noticed a Morricone-esque rift in the current background music), and the shooting is really satisfying.
I imagine it might grow old eventually, and it thus far does seem to have a good bit of shooting gallery style, but if so it's a shooting gallery you can run around in and it's pretty doggone fun.