It's OpenGL and can be run on less than DX9-class hardware. On my Radeon 8500 it looks a mediocre demo to me (doesn't look like screenshots and video). The farb-rausch demo that was recently discussed here and Rage3D is miles better (and is like DX7 or DX8 tech only)
It still does use DX9-equivalent things on the OpenGL side because my card didn't look like the screenshots. The last part with depth of field was the most impressive part, although it was buggy and very slow on my 8500.
Ahem, this is why I wish there was a sticky thread with this information. It would be nice to have this information kept at the top of the forum instead of having to search through thousands of threads.