It's fun but totally pay to win.
Also one of the most expensive cash shops i've seen
The design is really good, but really scary... The warframes, enemies, two-legged robots with no bodies or heads, the cube-head "crewmen"... Freaky! Fun but yeah I haven't tried any level/power-up stuff yet except some mods.
Interesting... Amazing how free-to-play graphics have come such a long way. And thank gawd, as always, I got a Kepler GPU. Best GPU since G80 series (8600GT etc).