Is there any unique features to this game other then it being an MMO?
To quote the developer(?):
I will also go right to the heart of the question a lot of players will have – “There are a lot of survival / Zombie games… how is this one going to be any different?”. First off, it’s a persistent MMO that can hold thousands of players on servers we host (yes there will be multiple servers with very different rule sets). Why is that a good thing? It means a thriving economy (oh yes… there’s trading). It also means you have potential allies in the all-out war on the Infected... and many an enemy as well. It uses our proprietary next-gen Forgelight engine and that means we’ve had a lot of really cool technology to work with to make the game we wanted to make. It’s also designed from the ground up for our players to become part of the design process. The Roadmap system that we built for PlanetSide 2 will be used extensively to clearly communicate what features we’re working on and what you can expect and when. You’re also going to be getting awesome access to our developers. We’ll be opening it up for Player Studio creations too so expect player-created items to make their way into the game. The main thing that differentiates H1Z1 from the other great games in the genre is the emphasis we are putting on player ownership and building. We want you to be able to form roving gangs that are headquartered out of an abandoned warehouse that you’ve taken over... or a house you’ve built from scratch after having cut trees down and secured the resources to make it. We are giving players the tools to make their own towns, camps and defenses, and they can decide how to set up their base (which is in the world btw... not instanced). We’re building in all the social features you’ve come to expect from an SOE game (grouping, proximity voice chat, voice chat for your gang, and many other cool social features).
To use a simple reference I’m sure everyone interested in this game will get... we want our players to make Woodbury from The Walking Dead if they want to. Or take over a prison. Or fix an old car so you and your friends (yeah we have multiplayer vehicles) can run zombies and players over mercilessly, and revel in the sheer delight of hearing a zombie scream as you light it on fire, or craft a gun to take down your friends and enemies alike. Our goal here is to provide emergent gameplay that will allow our players to make the world their own the way they want to. One of the best things about H1Z1 being an MMO is the fact that with a lot of people playing, we’re able to see all different kinds of gameplay. If you prefer a quiet life as a farmer raising crops... we’re going to make sure your zombie apocalypse fantasy is complete. If you’re like me and you want nothing more than to kill everything that moves, by all means see how that goes. It’s going to be a blast!
Tl;dr: It's an MMO. Anything you build will stay there. (build a house, house is just...there, like Rust). Claims they plan to have a map that covers the entire US (eventually, though I've heard that line before). Plans to support multiple types of play (cites farming). Claims massive player interaction, PvP, permadeath, active economy. Intimate interaction with the devs during development (going to have PS2-like roadmap). Seems like a mix of DayZ (zombies, player interaction) and Rust (construction, player interaction) slapped into an MMO.