Downloaded it over the weekend to give it a try and its pretty good so far!
Its a free to play 3rd person co-op sci-fi shooter with RPG elements. You are an ancient space warrior and it is your job to defend the solar system for some reason. To do this you have access to warframes which are basically organic looking suits of armour that each have there own set of special abilities. You embark on missions from your ship and enemies in these missions drop mods along with crafting materials. Mods can be installed into your warframe or weapons and provide bonuses and augments and the crafting materials are used to build new weapons and warframes. Each weapon and warframe ranks up as you use it which allows you to install more mods. To build new weapons or warframes you need to buy a blueprint with ingame currency and then build it in your ship using materials acquired from missions. All of the weapons and warframes can also be bought straight up for real money.
The combat system is very fast past and incorporates wall running and double jumping and generally feels very good. Graphics are decent too.