I shall review this game in a series of categories that all zombie games should have, namely:
Lag, Graphics, and all that.
1. Survival: 7 Days to die takes a very enjoyable path through surviving, you need to build structures, but you can't simply punch a tree to get the resources, so you have to scavenge before you can fortify, you need to stay well fed and hydrated to get anything done, which is really great, although the game does not incorporate things like anxiety and temperature yet. I hope they will, because those would be great. The Zombies can either be set to running all the time, only running at night, or not running at all, but despite the settings, you will eventually die. I once played a world where I disbled zombie spawning for a week, then set them to never run on the 8th day, and I died at 8:12 AM. I would give survival a 8/10.
2. Crafting: The game has an impressive crafting system, that you don't need a wiki for. You also can't simply create a house in the forest without gathering materials, to make a furnace you will need to either steal a pipe from another player, or loot one from a town. And to make glass jars, you will first need to find one to make a mold with. Unlike minecraft (Which too many parallels are drawn with), you need to find supplies to get better supplies, you can't just craft a gun out of iron ingots without a mold of the gun's components. Sometimes you will need to read a book you find to learn how to make something, (You can't make a wrench without a home repair book, etc. etc.) which makes the crafting feel so much more realistic. Crafting would get a 9/10
3. Character skills: These are kinda lacking in the game, as there is no current skill tree. Which I am slightly glad for. Most games seem to have a "When you kill X enemies, you can increase your knowledge, strength, agility, etc. Which will in turn increase your skills." Which is sorely un-realistic. A proper tree would involve doing an action to increase a skill, which would in turn increase your stats (Shooting a rifle increases your rifle skills, which boosts your marksmanship stat, Sneaking around zombies would increase your stealth skills, which in turn would increase your agility stat.) So if they do incorporate a skill system, I hope they do it that way. But for the current system, I would have to give a 0/10
4. Building: This is probably one of my favorite parts of this game, for it includes physics! You can't pull a minecraft and build a skybase, but if you do, you would need a ton of support beams holding it up. There is also weight in the game, if you stand on an unstable platform, or throw a heavy object onto one, it could collapse, potentially killing yourself and some zombies. I also really love the way you can use voxels to build houses, but the natural terrain will smooth out, making the hills and valleys look realistic. Building gets a well-deserved 10/10
5. Combat: This game has a decent combat system, with melee being your standard "Move in, click to hit, move out." technique, but the ranged combat is where things get a little funner. There is a stealth system, which allows zombies to see, smell, and hear you. Using a gun will make a lot of noise, which will attract more zombies, whereas a crossbow makes next to no noise whatsoever, allowing you to take out a zombie without attracting the horde. The zombies have a decent AI, nothing too special, but smart enough to sometimes avoid your pits-with-spikes traps you lay out. Using the physics in combat is truly enjoyable, (I really love putting explosives around the supports of structures and luring a horde inside, then shooting the explosives and crushing the zombies.) The only things that should be added to the combat would be improved melee, and the ability to make leaf-and-branch coverings over pits, making zombies less aware of them. Combat gets a 7/10
6. Game Customisation: You can either play on a prefabricated world, or a randomly generated world, you cannot create a custome world yet, but the devs have promised that. The amount of settings you can change on your world, however, is amazing. You can control everything from how long the days and nights are, how many airdrops you recieve, how fast you can open things, (Gun safes, cupboards, etc.) to how aggresive the zombies are, how much damage they deal, how long they will search for you if you sneak away, and even how many will spawn. Game Customisation gets a 7/10.
7. Multiplayer: I have not done much with this, but what I have done has been really enjoyable. I have gone on a server, talked to a guy, agreed to meet up, got sniped by his rival, respawned, locked out of a house, trapped in the open all night, found a city, met the guy, traded stuff, locked myself in his house, almost starved while he scavenged, found a gun in his house, teamed up with him, killed a horde of zombs, got bit, I told my friend, and so we started a search for some antibiotics to stop the infection, I almost turned, he killed me, took my things, and left me to respawn all on my own. The multiplayer is really great. The ability to friend people, making your house and coords visible to them, (And theirs to yours) seems to reduce the amount of betrayals, (You don't want to cross someone when they know where you sleep.) Making it a lot more enjoyable than other survival games like minecraft. Multiplayer gets a 8/10
8. Lag, Graphics and the like: The graphics are astounding, with beautifully rendered trees, disgusting zombies, smooth landscapes (The game was originally voxel based, so the smooth hills look beautiful) and amazing locations. It is all so realistic I greatly enjoy it. The game has detail, right down to the grass swaying in the wind. The only problem with this is that it creates an IMMENSE amount of lag. I can get good fps if I stay in a small location, or if I stay away from towns and forests, the ability to reduce video quality is also lacking, so if there was a setting that would cause trees and grass not to sway in the wind, as well as reduce particle effects, those of us who have wimpy computers would be able to enjoy the game so much more. Graphics and Lag get a 5/10 (5 For beautifulness, -5 For intense lag)
So all in all, I would give the game a 8/10 for epic zombie survivalness.