Looks like this could turn into a pretty nifty program. Not tried it myself (and yet to have a proper go at polypainting in Z3), but watch the videos, some nice things there.
"You can ask: Why is 3D-brush program necessary when there are such programs as Zbrush or Mudbox? 3D-brush is not intended to make a man out of sphere or cub. The main aim of the program is detailing and texturing the object already shaped in other 3D-packet. You work on detailing level equal to 3 to 5 millions of polygons. Operating speed of editing and viewing objects has grown bigger because of using a map of normals instead of geometrical splitting. It is well-known that it is easy to shape the object it takes several hours. But detailing and texturing is long process taking 3 to 10 times more time then modeling a draft itself. 3D-brush is made to make this part of technological process faster. The program contains options for sculptural modeling so that change of shape could also be possible. But the main function is detailing"