So far, I have tried these materials from Shapeways. Here's my pov.
Frosted Detail...Nice detail, but the texture is inconsistent. It varies from smooth to rough. No consistency. I wasn't fond of it, so I moved on.
Black Acrylic...segmented. fuzzy. Worst one yet for holding tolerances on simple shapes. Don't like it at all. Detail success rate depends on which side of the acrylic its one. One side is worse than the other.
Stainless Steel...if you are dead certain your print is done to your specifications, I rally like the Stainless Steel. Finished it has the look of a metal cast product. It looks porous but Im very happy with it.
Black Acrylite...pending...waiting on product ordered in this material.