Vaaary intersting...I just figured out what was up with Marble Clay - it's a spline modeler and doesn't use primitives...which makes me if wonder if this is meant to be more efficient than a modler that works with primitives.

I haven't actually tried modeling with 3D Canvas yet, the one that is getting me is Art of Illusion - its seems like a great program but I have yet to successful import any models or textures into.