So, here I am after playing quite a few hours (can't tell you how many as the game is not visible on my Xbox profile, but I guess at least 6). I'll drop some notes bullet point style, in no particular order. Feel free to ask questions, of course, and in case I'll happily try to answer.
Oh, a premise: I intentionally did NOT watch the 1hr long stream dedicated to single player, as I really wanted to experience the game directly, being genuinely surprised by the experience. So pardon me if some of the things I'll say might be obvious for you at this point.
• I think this game will be pretty divisive, as some of the base mechanics are pretty particular and not really that expected. Despite a not so memorable beginning, I'm definitely having quite some fun with it, but still I think this new iteration of Doom might not be everyone's cup of tea.... but I'll get to that.
• The graphics on Xbox One are really, really good. The world is detailed, rich and with lots of great effects all around, and thanks to the absolutely solid art direction the overall effect is honestly truly impressive. Even more considering that the game runs at 60 FPS, with no apparent slowdowns whatsoever (except for maybe one or two minor occasions while loading a new area, but absolutely never in combat). Unfortunately though the tearing is back (as it was in the Alpha), and it's definitely visible. I also experienced a weird problem during a mission, with one particular kind of enemy looking completely gray - as if the textures weren't properly loaded - and the ambient voices suddendly going silent: I had to quit the game and start it up again to make things right, weird. But again, apart from those flaws, the visual impact is pretty fucking amazing.
• I dig the art direction, a lot. At first it felt a bit too sci-fi and less satanical (even if the sci-fi was surely fascinating with its emphasis on heavy machinery and industrial settings, with some elements that reminded me of both Halo 4 and Warhammer 40k), but once you get to Hell... woah, you will not be disappointed. The character designs is equally great, I personally adore the designs of the various demons: they look menacing and grotesque, and it's super fun to tear them apart. And also, something that is a big plus in my book: the game is not afraid to use colors. Of course the palette will be mainly red and brownish, but the tones are super saturated, and here and there you will see some inspiring and jaw-dropping panoramas of damnation.
• The music is ACE. It's not always there, as when you are exploring it's mostly ambient effects and noises in the background, but when you start fighting and the soundtrack kicks in, it's fucking BADASS. Seriously, it's empowering as fuck, and it's another element that pushes you to be even more aggressive, more brutal and more lethal. Mick Gordon is really a beast (not that I had any doubt after the awesomeness heard in Killer Instinct!), and expect something beyond the crazy good industrial tunes. Gregorian chants in hell anyone?
• There is a lot of exploration: the levels are frankly pretty huge, elaborate and absolutely full of secrets. Lots of collectibles, data and power ups to find, and once per mission even some vey well hidden sections taken straight from the original Doom, with the graphics suddenly changing and becoming like the dream section seen in Wolfenstein TNO, to give you that sweet retro feeling (even if the enemy models will stay the same).
• To my surprise, there is quite some plot. Nothing that really gets in the way of the action, but I wasn't even expecting so many dialogues, little cutscenes and that amount of info regarding the lore. It's no The Last of Us of course (the main character is really just a dull shell, pretty much), but it's still entertaining... and it reminded me of Dead Space a couple of times (the tone is similar, and also some of the events, with basically hell unleashed on the surface of Mars)
• The RPG like progression of the main character is another element that took me by surprise: you are expected to explore the levels and fight with style (I'll get to that...) in order to become more powerful. By doing so, you will improve your personal abilities - i.e. more grenades, quicker weapon swap, better defense - but also your weapons (each of them has two secondary fire modes activated with LT, plus some other abilities like quicker cooldowns, more shells etc etc). It's nothing mindblowing, but it's a nice touch that adds depth to the experience (also because to fully max out a weapon you need to complete final special task like "kill 5 Mancubi with a Charged Rifle Shots" or stuff like that).
• The pacing and the way combat happens is honestly a bit weird, and I think that not everyone will enjoy this: you basically explore areas that are/feel more or less empty, then you get to certain points and... BAM! you fight like hell. Basically, enemies start spawning around you almost in waves, and you have to survive and kill them all to move on. Mind that you are not constrained in a small area (like a single room), yet the fight happens in a particular (and usually not so small) place, so you will definitely experience a bit of an arena-like feel. In that sense, the E3 demo with the Hell setting is really representative of the whole experience: the level is there at your disposal, and you have to be smart to use it at your advantage: some of the creatures will chase you, other will wait for you, others will keep jumping here and there... And you will have to simply bring mayhem all around, traversing the level at full speed, double jumping all over, hiding for just a couple of seconds inside a grotto, finding power ups and shells that are there to assist you in your massacre. The soundtrack will pump straight through your veins, adrenaline will rush, you will have to act smart and sometimes even improvise, judging what to do in a split second (which will result in either a beautiful victory or a shameful game over!) and there will definitely be blood. Like A LOT of it.
Once you've killed everyone, the enemies will stop spawning, so you will be completely safe and you won't encounter any more monsters in that area (which kinds of removes the tension IMO, but that's clearly the way they designed the game).
• Let's get real: as it was evident since the E3 presentation, there is a ton of emphasis on finishers. It's not just a matter of being spectacular per se (also because they kinda become the norm at the 27th Glory Kill agains an Imp), but it's also something that's deeply rooted in the game design itself. And, of course, that won't please everyone. Let me explain a bit how it works: when a demon is hurt enough, he will glow blue - with a very distinctive and honestly kinda annoying visual signal. That means you can perform a Glory Kill on him: if you are close enough by pressing R3 you will fuck him up for good with a quick and super gory finisher à la Mortal Kombat (the animation depends on the enemy type and on your position, and they are of course nasty and gruesome). A Glory Kill not only means that your opponent will instantly go down: it will also mean more rewards for you, like more health, other bullets and... more style points. Yes, because the game features - surprisingly, at least for me - a system that rewards you for killing your foes with style. Imagine something not too different from the one seen in Bulletstorm, even if a bit simpler: you can get up to 5 UAC shields per mission, and each one of them is used to improve your weapons as discussed before. So, willing or not, if you want to play well and become more powerful, you need to (ab)use the Glory Kills as much as possible. How much will you enjoy this, will depend solely on you: it's certainly a particular mechanic that pretty much defines this new chapter of Doom. Consider this: at times I found myself attacking purposely from a distance, in order not to hurt a demon too much, just to get the change to trigger the Glory Kill... Which is kind of a paradox, but still.
• The AI could be better. I'm playing at Ultra Violence and I think it's a bit on the easy side: opponents could be a lot more aggressive, more cunning, more vicious. At times they do feel like simple meat there to be slaughtered, frankly. Which is of course nice in a way, as you feel powerful as fuck... yet I wouldn't mind more challenge.
• Weapons are really good. Some are better than others (i.e. the standard gun and the heavy machine gun are not that useful, at least for my playstyle), but overall you get an absolutely rewarding sense of inflicted pain when shooting some evilish creature in the face. It's brutal, it's squishy, it's cruel, it's Doom.
That's it, at least for now... if something else comes to my mind, I will add more.