Yes it works with polys but in huge poly count in 5 levels of division,so you can jump from 1000 to 1000000 and back just by clicking.

As I understand it works in Z depth so it doesnt calculate polys in 3D and thats why is so fast and interactive...I gess.
Great for organic modeling, its like you're sculpting with a brush but it doesnt have a renderer so it best to use it with some 3D package like Maya.

Any way it is becoming one of "must have" CG tool.