Well, I played through the demo and here's my suggestions on the game:
1. Movement doesn't feel very fluid right now, there's a wind up before you start running at your full speed and a delay before you stop running. It's not a problem in combat, but is quite noticable outside of it
2. Enemy design/placement isn't particularly creative. Ranged guys should outnumber melee boys to force you to be more mobile and look out for more threats. In turn, melee ones need to be faster to be more of a hindrance when dealing with ranged guys. Spiders' damage is also quite low, you can practically ignore them as they probably won't even do 5 damage over the entire fight. You could also take after Dusk with how enemy grunts work-make them grunt only once per enemy type no matter how many of them are in the room, that would enable the player to identify the threats as soon as he enter the room and adjust their strategy accordingly
3. Rooms. This is kind of related to my 2nd complaint as the rooms are generally very claustrophobic and don't make for good arenas when your combat is so hectic and fast. Bigger fights are exceptions to this but smaller ones aren't
4. Setting. I really hope the rest of the game isn't going to be blood temples and swamps as that would get boring really quickly
5. Reloads. I don't feel like they belong in a quake-inspired game as the slowdown they bring breaks the fast tempo of the game
Generally speaking though, I liked the game. Locations are gritty and sound design is superb, keep it up!