"Poly modeling is better for more organic shapes like creatures, faces, characters, stuff like that, where tweaking and sculpting things is more important than cutting or slicing."

For now i agree, but nothing is impossible, isn`t it? You could do the base shape in a nurbsmodeller and then maybe do your detailing on some kind of second layer which is afterwards transformed into a displacement and normalmap.
The great advantage of nurbs is that you don`t have to mess around with a polygonmesh. You can create it after modelling. But in the end to replace polygon-modellers it`s all about tweaking faces, edges and vertices not necessarily on a polygon-basis.
Spaceclaim shows what is possible, but i think it`s only the first of several steps into this direction.

Only my two cents. Don`t really have the knowledge to give an accurat judgement, but my feelings say ->this is the way.... ;-)