Rick,

You are correct, we never explicitly stated the orientations (and the units?) of the coordinates and this is important. In fact, this was recently pointed out during the CIFTI discussions. CIFTI will follow the NIFTI convention and so should GIFTI.

If there is no disagreement, I will update the GIFTI document to state that positive X is right, positive Y is anterior, and positive Z is superior. In addition, the units of the coordinates are millimeters.

John