My 2 Dinars here (Currency used in Serbia).
The stuff from Shapeways is a little grainy, even there premium finish which was then called Smoothest Fine Detail.
They now have another which is supposed to be even finer and smoother.
Attached are some pictures of a mid engined 70's era race car tranny that I just had to have. I had several of them but they all burned up so I don't have the ability to take pictures of the raw product from Shapeways but like I said, they were a tad grainy.
I applied several light coats of Alclad filler/primer diluted using Gunze Leveler. With a bit of very light sanding in between coats.
While its expensive, some stuff I can only find there, like the fore mentioned tranny.
PS One can make anything work and Randys/MBWH upcoming spoked wheels look awesome, plus he's become a good friend so I'll for sure buy those from him and just abut anything else for that mater.
PSS I do agree with Dan though, 3D printing can be grainy and pricy but that's ok with me. I wished everything was of the same amazing quality as HRM fromage which is good old fashioned resin casting.