Now that I have gotten all achievements and have completed the game 100%, I feel like I can leave an accurate review. Let's break it down just like the main menu does.

Campaign
Positives: Some might say it was short, but if you go searching for secrets and challenges they you can end up sinking quite a bit of time on the levels. The combat was very fluid and tearing an imp's face in half is really satisfying. There are plenty of glory kills to experience as well, so approaching from different angles just to see how they die was a real time sink of mine. (Another time sink was just looking at the scenery, especially in outdoor levels.)
Bosses were actually really well done. You need to see attack patterns and dodge, attack when the time is right, and when you do, attack hard. Glory kills on bosses were well worth the effort of the fight, too.
The best part of campaign is that when you find a classic doom map secret (there is 1 per level) you unlock the full level to play on the new engine from the campaign menu.
Overall the campaign was gorgeous and really fun to play. It is the crowning achievement of the title hands down.

Negatives: Most negatives I have are simply bug-based. Sometimes progression on a challenge would not save, often the game gives and errorless crash. Another time, I was glory killing an enemy, and fell through the map and died. These types of problems are killers if you are playing Ultra nightmare. (If you die, you're done. It even leaves your helmet behind with your name and how you died as a warning to players, or just to laugh at someone's misfortune.)
A complaint that I had was that some enemies only had maybe 2 distinct glory kills, while the lesser demons like imps have upwards of 5.
The biggest negative of all was the lack of Co-op campaign. It was beyond frustrating but I understand that the campaign was built for only 1 player. Maybe next time design it as such where co-op is considered from the beginning? (Yes, I know it was stated before release that campaign would not be co-op.)


Multiplayer
Positives: This is where most people are complaining and I have to say I can't disagree with what they are saying. What I can say is that if you get your team in a group and they stick together the whole time, you will decimate any poor enemy player that happens to walk by your horde of marines.
Every gun is good in its own right but ones that stood out to me are the chaingun and lightning gun. Like any game, however, a determined player can master a gun and run with it.
Becoming the demon is very satisfying. You get a rush of "LOOK AT ME NOW!!! HEY! REMEMBER ME FROM EARLIER!?" as you leap through the air as a prowler and snag some poor guys head to slam into the wall.
The fast paced environment is also quite hectic. Explosions, lightning, plasma, bullets and demons all at once can make for a ridiculously dodgy, fun time.

Negatives: Here is where I see some design that I wish had been done a little differently. Balancing is sometimes off. For example, you wonder why your team is losing 60 kills to 30, then you press tab and see that they have almost twice the amount of players that you do. I wish they did a better job at populating those empty team slots mid-game.
Guns feel overpowered/ underpowered at the same time. Ever wind up the chaingun and start getting hits on a guy, and while he is being hit, he winds his up and kills you first? Yeah, that. Though, in other instances, I go on a 6 kill streak with the thing. (On a side note, 2 players with lightning guns can take down an army at close quarters.)
Getting the demon rune is almost completely random. Maybe it spawns near you, maybe the entire map away. Maybe its always around some corner where an enemy is already grabbing it to kill you. Maybe you get killed as you are about to grab it for the first time in 6 matches. All of this happens on the regular.
Guns need variety. There are a handful of them and you cant even choose the attachments like in the campaign. For example, I only really use 2 loadouts because I can't put a grenade launcher on my combat shotgun so I dont need another shotgun loadout. Get what I mean?
You also unlock them super quickly. In an afternoon you have unlocked basically every weapon and demon. There will be 3 more multiplayer packs containing maps (it needs more), weapons, (it needs more), and demons (definitely needs more). Oh, and more customization for your marine. All in all its negatives don't feel like enough to make me NOT want to play the multiplayer.


Snapmap
Positives: I actually had a really fun time using snapmaps. There is a lot of potential here and I can't wait to see what some creators can make. I have already published 2 maps myself and one of them I am quite proud of. (A co-op survival/ escape map with weapon and equipment shops.) The logic and flow portions are honestly the most fun, too. I could potentially make a king of the hill map for example where there is a demon player, and a timer. If I wanted, I could make it such that killing the demon makes you the demon. If you are the demon at the end, you win.
Executing the logic is quick and easy too. You can test the maps before publishing as well which is nice, and if you happen to notice something you want to change, simply re-upload and it will replace the old version of it, regardless of name change. That is probably my favorite feature so far.
Tutorials are really easy and the puzzles are there to show you a few more examples and give you ideas and are really fun to complete. There is no shortage of reference material either. (There are youtube channels dedicated to snapmap tutorials already, so even if you can't figure it out, the answer is probably out there.)

Negatives: Co-op test play. It doesn't exist. If I want to test a co-op map, I have to publish it (i usually put beta in the title), then host and test with a friend, find a problem, go back to the editor to fix, and re-publish. Note: they side- stepped this problem with the republishing ability, so I doubt it will be changed.
Weapon varieties could be more diverse as well. If I want my team to start with the siege version of the Gauss gun, I should be able to put it in my map. If it's in the campaign it should be in the editor. It's not like a lot of competitive gameplay is going on in snapmap.
Another complaint I had on snapmap is that there werent any rooms from classic doom. You tease us with classic model options for keys, but don't allow classic rooms.

Overall, these shortcomings don't even put a dent in my opinion of the game I love it and feel it earns its spot in the Doom library.