Warframe has been in development for quite some time. I found their site and registered for beta access since a few months ago. Now, they've started the closed beta testing phase and I can show you how great this game is.
Warframe is a co-op free to play third person shooter with a pretty decent melee mechanics developed by Digital Extremes(The Darkness II) with the Evolution Engine. Where other shooters right now usually only have melee attacks as an afterthought, Warframe actually have interesting melee attacks and it looks great too. Some people says that it looks like Mass Effect 3 multiplayer and I'd say they're wrong. The game handles melee attacks better than Mass Effect 3. I enjoyed Mass Effect 3 multiplayer but this game offers a different experience.
Co-op, the game focuses more on co-op gameplay rather than PvP(in fact, i don't think PvP even exist right now). This makes me really really excited for it as I always prefer PvE than PvP. The areas shown in the videos looks quite expansive and the graphics looks really great. What's even more amazing is the fact that it plays smoothly on my old PC, really great performance optimization for a game still in Closed Beta, unlike a few other titles I won't say here.
Warframe offers plenty of customization options with 8 Warframes currently available and plenty more will be added later on. Each Warframe will have different playstyle and abilities, every one of them looks great. Each Warframe have different upgrades which you can choose as you level up.
There are also various kinds of weapons that you can choose to suit your playstyle. As with Warframes, weapons will also level up as you use them and each weapons will also have upgrades which you can choose, from rate of fire, damage and even mod slots. And yes, weapons will have various mods you can stick in to make them even stronger.
Now if you've seen the trailer for this game you'd notice the soundtrack, which is awesome. I like the Japanese-style soundtrack they used for the game and it really goes well with the whole aesthetics of the game which has this Japanese sci-fi feel to it.
The game also have a Crafting System where players can collect various parts dropped by enemies to build weapons or even warframes(if you have the blueprints) in the Foundry. Most weapons can be bought with in-game currency but Warframes can only be bought with platinum. I'd say it's a pretty fair deal but the current price for Warframes are quite high(some higher than $10). I'd say they need to lower the price for each Warframe, especially if they plan on adding more Warframes in the future.
What worries me a little is the fact that you can unlock more upgrade options for Warframes and Weapons with real life currency. I'm afraid that this will ruin the balance and differentiates free players and players who pays. True that this is a co-op game but when they release PvP mode(which they should) this'll be a big problem because it's definitely pay to win. However the upgrade cost is quite cheap though(around $1-2) so it might not be a big problem.
For those of you who are interested in trying, check out their site https://warframe.com/ and register for the beta. You can also buy the Founder's Pack to get instant closed beta access.