To try out the 'Full Color Sandstone' material at Shapeways, I ordered a print for a simple but obviously colorful test piece.

The material kind of feels like a small rough piece of delicate wood to me.
Physical detail seems to be pretty good, but I get the impression that the 1024px (about 850dpi) color texture I included got downsampled to around 128px (about 100dpi) or something, because there are visible loose pixels where there are supposed to be thin lines.

The circle is 3cm diameter with 3mm thickness, the small border on the side is 1mm.

Here's a picture of the top side:
Color Top

And here's one of the bottom side:
Color Bottom

As you can see, if you compare them closely, the bottom side shows printing lines, while the top side surface is perfectly flat.

Also, here's a picture with backlight, showing some slight transparency on the thin border:
Color Backlight

An interesting effect of this bit of transparency, is that you have some minimal subsurface scattering in the lighting of the object.

To get around the downsampling issue, I think the safest choice would be to disconnect the texture UVs completely whereever you need to texture a sharp shape in your object, so that the colored shape is polygon based and not bitmap based, and only really use the texture space for soft color detail.

The color quality remains quite close to the original texture colors, but is slightly more yellowish for some colors.

When dropping the object on the ground, only from the 1mm border break off small pieces, the 3mm seems to be strong enough to survive that.