Call of Juarez: BiB is a game with lots of small twists, but it's your run-of-the-mill shooter at heart. It doesn't quite pull the whole package off, but it comes quite close in many cases. The gunplay is fun enough to last the length of the game, in part because you have two different characters to choose from every level, a fun use of gimmicks (like the showdown minigame) and a wide selection of upgradeable pistols, rifles, shotguns, derringers(!), knives and bows to murder people with. Oh, and because it's quite short, about five hours.
Really though, Call of Juarez is about shooting people in the head (or, in showdowns, in the family jewels. You'll see.) Full stop. If that kind of game isn't your thing, neither is this game. For you, my verdict is: wait for a demo to be released, then Demo It.
The gunplay is somewhat similar to a zombie shooter, with enemies being weak but quite dangerous in numbers, small clip sizes and constant reloading.