I actually ended up playing this for free with the 7 day PS Now trial, in preparation for Doom Eternal. It was much better than I was expecting.

Pros:
+The action is so fast paced and explosive. It's some of the most fun single player FPS I've ever played.
+Menu shows total amount of collectables in the area so you can know if you’ve missed anything
+Constant upgrades left a great feeling of progression, speaking of which:
+The difficulty curve was perfect. I always felt I had the same level of "just right" challenge. This is partly due to the upgrades mentioned above, and also the introduction or more and more enemy types.
+The weapons for the most part don't suffer power creep. Thanks to the upgrade system, even the starter shotgun was useful to me well into the end of the game.
+Multiplayer is fun, even if it doesn't do much to stand out from every other FPS multiplayer.

Cons:
-The map is absolutely horrible. If you're using it to try and find out where the collectables are, you're going to struggle through the lack of any indication of where walls are, making the different rooms and floor levels impossible to tell where you can get to room A from room B. You also can't zoom or pan much further than where your icon is, so if you're trying to look for where that one collectable you missed is, you're out of luck.
-Some levels are arbitrary point of no returns, which goes against the entire of exploring every nook and cranny for secrets and upgrades. It wouldn't be so bad, but thanks to the huge open-nature of the stages, and the horrible to read map, it can be hard to know exactly which parts you can get to at the current moment, and which parts will be locked out if you go through this door and it locks behind you.

Mixed/Not important enough to be a pro/con:
~I ended up with a glitched trophy that didn't pop, preventing me from getting the Plat without playing the entire game again. While a glitch is a clear con, the fact it only affects the trophy system, which isn't technically part of the game, means I can't give the game a con for it.