Simply amazing. It's glaringly obvious that the devs have played old classics like Quake, Quake II, DOOM, DOOM II, Unreal, and so on. It has that old school feel to it, but with a modern touch.

+ Level design was brilliantly thought out, very well done.
+ Secrets are VERY well hidden in many cases, but not to the point where they make entire submaps just to hide a secret; they're challenging to find, but fair as well.
+ HIDDEN SECRET BONUS LEVELS!!
+ Horde mode is fun, and actually challenging.
+ No hand-holding. Everything is a finite resource, and you have to spend it wisely. But at the same time, the combat is fast, frantic, and furious.
+ The enemy designs are ranging anywhere from classic to borderline inspired. Many of the enemies' first appearances filled me with dread, terror, and horror, as I struggled to survive against the unknown horrors lurking in the darkness...and then, later in the game, I simply smirk as I see those same enemies, blasting my way through them like a total badass...only to find something new to fear, even until the very end...
+ The level design is freaking BEAUTIFUL.
+ Hey, did I mention how much I love the level design?
+ The story starts out strange, abstract, and confusing. Then plays off of that and uses the player's lack of knowledge about the world of DUSK in a kind of meta way. And then all is revealed at the end in an amazing final confrontation that made my jaw drop below the floor the first second I started that fight.
+ Dude. level design.
+ All the weapons are unique and important, and I very often found myself using all of them at least once in almost every level.
+ SNIPING WITH DUAL SHOTGUNS!! WHOOOOOOOOOOOOOOOOOOOOOOOOO!!!!!!!!!!! :D
+ The sickles idea for a melee weapon is unusual, creative, and cool. I like that.
+ THAT LEVEL DESIGN THOUGH~.... xP
+ Mama still scares me. :-:
+ Dual shotguns, Dual pistols, Dual sickles, you name it; Dual wielding is just...SO awesome!
+ Full auto rocket launcher? MAXIMUM....POWWWWAAAAAAAAAAAAAAAAHHHHHHHH!!!!!!!!!!!!!!!!!
+ "The voice" sounds really, really cool.
+ Btw, the levels have such a nice range of colors and styles...it SCREAMS of Quake I.
+ No, I won't stop going on and on about the level design, 'cuz it's frickin' GREAT!

- It's cool an' all, but I really just don't like the countergrav powerups; having gravity switch around on you reminds me of Crazy Gadget, and I HATED that Sonic level....
- Not enough levels. I mean, there's LOTS of them, don't get me wrong. BUT I CRAVE MOOOOORRRRRREEEEEEE....
- The Sword is OP when things are already too easy, but borderline useless when the you-know-what hits the fan. It's cool design, buuuut not as good in action as it is in application...
- MAMA IS WATCHING.
- The first episode is a little 'too' easy. Granted, it's meant to teach new players how to play an' all, (And on that note, it's nice how there are no tutorials.) Buuut....ehhhhhh......all in all, things start getting cool in episode two. And mind-blowing in episode three.

FINAL VERDICT: 9.5 OF 10
I wish I could give it a 10 out of 10, buuuut they really need to work on adding more episodes, more levels, new powerups, more enemies, and LOTS more Horde mode maps. Other than that though, it's a beautiful, wonderful, amazing work of art.
At first I thought all the hype for it was just a bunch of advertising campaigns, but in the end, y'know what? Believe the hype. Buy this game. I'm serious; this game is so good, I'm amazed I didn't play it sooner. I promise you will find a non-stop thrill ride from start to finish. I don't just recommend DUSK; I say HELL YEAH! If there was a double-thumbs up, I'dve picked that one in a heartbeat.