Rust is one of those early access games I had kicking around on my Steam wishlist, and finally picked up last month.
The most apt description would be to call it a cross between Minecraft and Day Z, with the scales tipped towards the latter. You start out somewhere in the wilderness, completely naked with nothing but a rock, a torch and a couple of bandages. With this versatile rock, it is up to you to survive.
By bashing trees and other rocks with your rock, you can collect wood and stone/ore bits, and thus begins your slow climb up the technology tree. Armor, melee weapons, guns and even structures are yours to amass.
I find that this element of construction gives the game an edge over Day Z for me. Your character is saved server-side, so you cannot simply hop from world to world with your progress like in Day Z. Instead, you attempt to carve out your little piece of the countryside amidst a persistant community.
Some servers even offer a "sleeper" feature, taking the persistant world to another level. When you log out, your character does not disappear. Instead he lies down on the spot and goes to sleep until you log back in again. Obviously this raises the stakes, since you can be killed while offline, but I enjoy the added tension.
The player element, as is typical in games like this, is Rust's biggest wildcard, and ensures that everytime you play, and every server you play on, is going to offer a slightly different experience. With games like Rust, and Day Z, I tend to enjoy them more when I approach them as a roguelike, rather than an MMO.
That is to say, instead of thinking that I'm going to farm up this awesome guy with lots of gear and then being irritated when I get killed and lose it all, I just try to see how long I can survive, and then try to beat that record. Try different strategies. And most importantly, take a few days or a week inbetween play sessions.
Starting from scratch repeatedly in a short timeframe is frustrating. Once it a while though isn't so bad.
The game does have zombies, because all games have zombies now, but from what I understand, they're just a placeholder. Hopefully that's true, and the devs replace them with something a bit more interesting in the future.
Rust and Day Z standalone are both attractive games, and both in rough alpha stages with a long way to go. Day Z has the name brand appeal, but right now I think Rust offers a more immersive and entertaining experience by letting players actually make a mark in the world.