I was going to use Poser/Blender to do some head sculpts but I was looking for a 3d Printer that has the detail to produce them with as little clean up work on my end as possible.
Mudbox is fairly popular and sculptris is an AMAZING free program from the makers of Zbrush.
The shapeways stuff looks like it was printed with a objet. Look for someone who uses a perfactory printer.
MUCH better results.
I use Visionproto in Texas. His perfactory machine is great. I had a head model of an elderly woman printed as a test and it came out 1/12 instead of 1/6 (measurement issue with the file) and the detail was stunning.