Pretty positive on the demo.

Visuals are very good and the game runs well for these indoor areas on an older PC. Biggest strength of the game is the dark atmosphere. Gunplay feels good. The demo has good level-design and does a good job showing the functionality of buttons.

Things to fix are the huge ragdolls being in the way of gunplay / pickups, settings not saving on death, and no auto-saving.
Weapon-switching can be improved upon with distinct animations and sound-effects. Right now it doesn't feel satisfying to switch weapons.
Be wary that models can block player projectiles, for example the metal pillars in the final area.
A concern I have is that all enemy types have had linear pathing towards the player.