Text adheres to the same 0.6mm wall and gap rules that govern other features for 3D printed parts. With letters that contain knife edges and other acute angles this can become a little tricky.
We went to Thingiverse to find a great file to test the accuracy of printed text in the 3D printing processes in which we see it most: Selective Laser Sintering, Fused Deposition Modeling, and Polyjet. Our text test file was contributed to the Thingiverse by the user GreySamson (http://www.thingiverse.com/thing:383163).
SLS Nylon Results
Lettering and spacing clear and crisp down to 0.43mm letter width.
FDM ABS Results
Lettering and spacing clear and crisp down to 0.83mm letter width. Outer walls of text shown 1.04mm - 0.83mm, but inner area of text not filled.
Text becomes a little bunched together at 0.22mm, but text fully resolved throughout test part.