Warframe has no official release date, but you can participate in the open beta via Steam, or as a download from their website.
I'll be blunt. The game is fun, but nothing too impressive. The character movements for dodging and wall-running are neat and the game looks pretty nice given the hardware I use, but if the game had done a bit more to innovate and add flavor, if even just to spruce up the otherwise bland art direction used for the level design, I'd be all for it. As it stands, it's a bit on the generic side.
Here's N and I, discussing in detail what Warframe is, as well as our thoughts on the experience.