I tried the demo, it is indeed very good. It has a tactile solidity to the whole thing which makes it feel very immersive, and yes even the basic gun is great, but once you get use to firing and reloading the better weapons it really takes off. It has the best barrel explosions I think I’ve ever seen. The demo is basically the same two sewer levels (although randomly generated) on a loop of increasing difficulty. The only thing I’m not clear on is how the full game differs in terms of variety.
The only downside is the smooth turning is anything but to my eyes, it has an unpleasant jitter which doesn’t do much for my stomach. Smooth stepped turning is better, but slightly awkward.