Beat Boltgun tonight. Played on Hard difficulty (3rd of 4 options). Took me 14.4 hours, according to Steam.
Not a perfect game, by any means. But it was really enjoyable. If you're either a fan of the 40K setting or a fan of boomer shooters (OG Doom), I would recommend. Definitely scratches the itch for a FPS with a wide arsenal of crazy weapons that mostly feel unique, big set-piece fights, collecting power-ups, dodging projectiles, a variety of enemies that all require different weapons or strategies to deal with, collecting colored keys, 90s charm, and tons of pixelated gore.
The cons (list will be long, but most are relatively minor):
*Difficulty is super inconsistent, thanks to dumb enemies. The big encounters and boss fights can be really hard at times, but the enemies just normally spawned around the environment are mostly jokes if you're willing to play patient. Granted, if someone was trying for speedruns and whatnot, these enemies would be a bigger challenge.
*If you're able to find the vortex grenade on each level, it can turn giant bosses into kinda jokes. It is a secret item, and usually the hardest one to find on levels, but if you get it and save it for the next big baddy boss, it chunks like 50% of their health.
*There are a number of levels that you can definitely get lost in. Rooms within levels often look similar, and it's not always obvious which hallway you should be going down next. Even after you find the required path and keys, sometimes it can take a while to backtrack to the locked door.
*A handful of level suddenly have platforming sections, and the jump controls aren't tight enough for it to be fun.
*Once you have a bunch of weapons, it can be annoying to scroll to the one you want in a particular moment and can lead to panic moments.
*They show you a dash ability to get thru a closing door in the first level, but then never require you use it again.