I've heard good comments on parts printed by
http://www.moddler.com/ Both print a Part and Moddler list resolutions at 600 dpi/ .0016"
Moddler also states their Z axis resolution is 1600 dpi.
Shapeways does not list a resolution or dot size, they do list a minimum detail size of .2mm/ .0079"
As a comparison the average human hair is .003-.005"
Moddler also has a price estimate tool on their site.