JMO, but the 3D layer in photoshop CS3 was terribly implented, hardly worth the trouble.

Poser meshes are generally massive, and so if you do manage to load it, will make the whole thing painfully unresponsive.

all in all,  not worth the trouble. I gather  3d layer works better in newer versions of photoshop . . . but if you want to manipulate giant meshes and paint on them, Zbrush or Mudbox is much, much friendlier. Deep paint is an older application, used for this too.