I bought HudSight to use it in DOOM Eternal.
DOOM Eternal has 2 crosshair options:
1. A visually well-made default crosshair which changes with your weapons and gives you additional information. The only problem - it doesn't display a dot in the center for precision shooting.
2. A dot. Nothing else, no additional information, no dot customization.

Now, I want to have a small "dot" in the center - that's how I aim and make micro-adjustments. But I also want the nice crosshairs the game offers me.

In comes HudSight to the rescue!
With it, I modified their "cross + dot" sight into a simple dot sight, scaled it down to 50% so that it's just barely noticeable and went to town on the demons.

I could not believe how better the game felt and how much more confident I was in my aim. Mind you, I aimed perfectly well without the dot, but it just adds a layer of confidence to my shots that I was missing before.

I'm a developer myself and, while I COULD make something like this on my own, the "cup of coffee" price I paid for it makes it more than worth my money and the time-save it provided me.

Thank you Mr. Kozadaev - this is a remarkably simple yet effective tool!

TLDR: DOOM Eternal is first-person shooter perfection.

I'm a fan of DOOM and Quake. I'm a fan of arena shooters in general (Quake Live, Overwatch etc).
I've thoroughly enjoyed DOOM 2016 and found it to be the best revival of an IP that I've seen.
I expected DOOM Eternal to be more of the same, maybe with a few tweaks here and there.

But, holy cow, nothing could have prepared me for this.

DOOM Eternal upgraded on every single aspect of its predecessor. It's everything I wanted in a DOOM game, and then some.

The combat is unrelenting and fast-paced, yet cerebral at the same time. If you are not constantly thinking and making decisions, you are dead, especially on higher difficulties.

The arenas feature a lot of verticality and perfectly complement the weapons and movement options at your disposal. There is a huge variety in environments and you will not find yourself getting bored with the looks of the game. As soon as you've had your fill of one environment, DOOM Eternal makes sure to teleport you into something completely new.

The demons are well-varied, extremely aggressive and smart. They all behave differently from each other and you will quickly learn to distinguish between even the weenies. And you will have to if you want to survive - the weenies, while being made of paper, can still dish out significant damage.
Some of the demons have weak points and destroying those weak points is oh-so-satisfying.

Between fights there are short platforming sections, none of which are terribly hard. They give you a chance to play around with the movement and take a breather before the next arena-slaughter. They are also when you will explore and find various upgrades and collectibles. 100%-ing the game isn't terribly hard, but it's very rewarding nonetheless.

The sound design is superb.
First off, you get Mick Gordon's brutal metal soundtrack. It's not just a soundtrack though, it flows between each combat encounter, reaching it's peak during peak slaughter and lightly riffing in between fights. Every map has its own soundtrack with multiple plays on the main theme of the soundtrack.
The sounds themselves are excellently created with each action having its own easily recognizable sound. This allows you to focus on the action and simply hear when something in your arsenal is ready, or if that off-screen grenade has succesfully removed an enemy weak point.

There's a lot of fan service in DOOM Eternal - from the monster designs looking like DOOM II/64 sprites, the skins and collectible figures and albums. But this doesn't in the least detract from the experience of the game. It's a love letter to the older gamers who grew up on this, and it's a way for newer generations to be able to appreciate DOOM's roots.

In the end, a word of advice:
You will want to play this game on Nightmare.
You don't need to do it in your first play-through, but do yourself a favor and try it out once you're familiar with the game.
I promise, you won't be able to play it on any other difficulty afterwards.

I've thoroughly enjoyed DOOM Eternal and I'm still playing it as of writing this review.
It's my choice for Game of the Year 2020, and I feel that it will last me a while longer than that.

Buy this game, especially now when it's on sale. You won't regret it.