This game was pretty damn good I must say. Playing this not long after playing through the original Doom, I can say that this game is a worthy successor to the progenitor of mainstream FPS's.
The game wastes almost no time getting into the action right from the get go. While there is a story to the game, it's pretty much non-essential to the core experience and isn't too intrusive to the game.
The combat is, taking it from face value, is very similar to how Doom originally was. However, playing it has proved to be a pretty unique experience. Combat is just as fast and frantic as it's predecessor, however, it definitely feels like a desperate fight for survival. Enemies are numerous and aggressive, and Doom Guy himself can't take too many hits from enemies. Performing "Glory Kills" cause enemies to drop health for you. Which is essential to survival as there is tons of shit flying at you. I played on Ultra Violence and died numerous times throughout the game. Which I found pretty surprising as I probably died more times within the first three or so levels in this game than I have in the entirety of Ultimate Doom.
With the addition of jumping and grabbing ledges, the game also has a bit of extra depth to it. Environments are designed with platforms, ledges,nooks, and crannies everywhere at various heights. Which adds to the game's combat in that they can provide a way to get out of potentially nasty situations, and also adds to the exploration by having ammo, power ups, and occasionally secrets. The levels feel like large playgrounds.
And while I'm generally not big on how a lot of modern AAA games like to put in an upgrade/RPG systems within FPS's, here it actually adds to the game rather then feels like something tacked on for the sake of it. In order to upgrade your weapons and armor, you need to earn these items by essentially doing what Doom does best: Killing stuff and exploring the levels. Each level grants you weapon mod upgrades for killing enemies, finding secrets, and fulfilling the optional challenges.
The different mods for each weapon are pretty sweet and for the most part, useful for different situations. With the possible exception of the remote detonated missile for the missile launcher. Can't really think of any instance where that could be helpful.
The levels themselves I felt were awesome and really well done. However, some levels I felt were a bit too linear at times. Sure, the levels can seem really large, especially if you look at the auto map. However, the way progression works in this game kinda feels like you're following a set path rather then having multiple paths to choose from. That's not to say this is like this for all the levels. There are a select few however, that could benefit from having more than one path to choose from, being more open, or at least have a better sense of interconnection.
I also really dislike how there are several points in the game where once you go past a certain point in a level, you cannot go back. This isn't really so bad on repeat playthroughs as by that point, you can become familiar enough with the levels so you won't miss any secrets. However, on a first playthrough, these are often not so pleasant surprises.
I also found it kinda strange there was an upgrade tree which made finding secrets easier. Doesn't that kind of ruin the point of finding secrets? Not that that's a huge deal, as it is optional, still, I think it would be nice if the developers had a bit more faith in their players in this regard.
I also love the sense of humor the game has. From Doom Guy smashing stuff he's told to handle gently, him fist bumping a toy model of himself, and him giving the thumbs up to the player as he sinks in lava gave me quite a few chuckles.
Also, I LOVE the amount of violence and gore there is and how well it meshes with the game's fast and visceral gameplay. All the different ways you can execute an enemy depending on where you're attacking them from, the different ways their bodies react depending on where they're been shot, what limbs or body parts get blown off, or getting killed by a certain weapons. Would have been nice if the bodies stayed on the ground, but I'd imagine that is probably due to the sake of performance. Also, the many ways Doom Guy can die are also entertaining to watch.
Overall, this was a great game and a worthy successor to Doom. I highly recommend it and I hope this gets a sequel.