The word "Frosted" is very important here. The items are NOT "clear" as in "see-thru" The exterior surface is actually "Frosted".
I've got some pictures here comparing FUD to WD:
https://picasaweb.google.com/stonysmith/ShapewaysUltraSmooth #
I would post them here, but Picasa allows you to zoom in to the full resolution of the images.. lint and all. One note: the items here were designed for WD/BD/TD.. and have not yet been re-designed for the new thinner wall options. The trucks pictured are approx 2cm long, 1cm wide. TINY stuff.
As shipped, FUD could not be used for lenses, etc. I have not yet had the opportunity to see if the surface can be altered to make it completely transparent or not. (I sent all these items off to my painter friend)
I have a suspicion that if you apply a thin coat of liquid glue to the surface, you may be able to get it to be "almost" see-thru, but due to the nature of the process, I still expect the internal index of refraction is going to change from one layer to the next, causing a scattering of light, keeping it from ever being truly "clear".
As you can see in the pics, the old WD/TD material was always a bit yellowish... this new material is much closer to truly colorless.