I know I'm probabably singing praises too much and there may be eventual community backlash, as is the rule of initial positive impressions.
But I wanted to compliment the overall design of the game. It's pretty much a classic example of the whole being greater than the sum of its parts.
For example, take the mechanics. As I think the RPS review pointed out, it's the sort of thing people, like me, probably tend to avoid in games. Single-player, linear experience, a bunch of setpieces, regenerating health, blood splashes on the screen, automatic checkpoints, QTE's in places. How modern can you get, right? And yet they still let the player have fun, a LOT of fun sometimes. The shooting is pretty good, the guns are satisfying (though the normal shotgun could probably be more dramatic), the cover works acceptably.
Take the QTE's. QTE's are awful right? Except the ones here (I'm talking about the WASD ones, not the duel ones) have a few things going for them. One, if you fail you don't instantly die. If you press the wrong button for a guy who popped up behind you, or you mess up a chain of four guys surrounding you, you still keep playing, and you take them out the normal way. It's just a bonus. In one case someone popped up behind me, I hit the right button, and instantly spun and shot him for a Reflex bonus. That makes sense to me, game-wise -- you might sometimes have moments of instinct to take out someone sneaking up on you. Then three, still about QTE's, sometimes (always?) if you fail you have to pass a secondary test, which might be related to the sense of death thing you can charge. You get the slow motion bullet dodge. This is not hard, though I have occasionally screwed it up, and it's fun to do, and it at least sorta makes sense with gunslinger reflexes. And of course the enemies talk about it too, like "what the hell just happened, did you see that?". So all in all, they're not purely arbitrary, instant death, they're relatively fun, they're not overused, and you can play around them. They're sort of like QTE's done right, if you have to have them.
For another example, take say, the secrets you find. In some games, hunting secrets might be some pure filler to collect orbs, but these not only relate to the chapter you find them in, but they tend to have art from the time period, have an actual presumably true little story, and may even be interesting. They're cool things to pick up. The overall graphics design is pretty consistent (I say this not being a designer myself, just saying it's pleasant and doesn't feel disjointed).
For yet another example, take the cutscenes. I mentioned that the ingame models do not move their mouths to talk as far as I'm aware, which presumably helped the budget a little. Mirror's Edge is one of my favorite games, yet people criticized it for the cheesy animated cutscenes. That's a legitimate criticism, and it was jarring considering how the few first-person cutscenes they did were actually pretty decent. In Gunslinger, the cutscenes are entirely 2D. I think there is a technical term for the film technique they use or approximate, though I do not remember it. They move the camera over/zooming into static images, with maybe a couple of separate parts so different parts of the image shift. No animation other than that. And yet, the art is GOOD, and the voice acting is so fitting that it works pretty seamlessly with the normal gameplay. Lastly, the loading screens appear to be ingame captures, but with filters applied in such a way that they almost look like sepia tone photographs. They use a similar thing when gameplay pauses for narration changes or breaks, and it's pretty effective.
All of these things are small polish details, and might be lame if used by themselves, but the overall package is very cohesive and I'd like to think a lot of love went into it. I wouldn't want every game to be a linear shooter like this, but if you're going to do it I applaud this sort of design.