Thank you Daniel for your great work. While bringing up my new Chaucer printer (see http://www.thingiverse.com/thing:33636)http://www.thingiverse.com/thi..., I was able to successfully print the 2x4 test block. I've not yet applied your recommended settings, as I'm still calibrating the basics, all at 30 mm/s.
I was able to fit the printed part to a factory part on both the pin and socket side. After a few snap in tests, I broke one of the socket cylinders on the printed part. I will switch to your recommended configuration settings, but in the meantime, have you broken parts before? Wondering if my parts are slightly undersized.
Also, has anyone heard anything from official from Lego about the 3d print community making Lego compatible parts?