I've never used timing belts (cog belts) on a first machine before, but use em a lot around work. They work very well for high transmission energy, minimal backlash, high accuracy situations. Have a linear positioning table using a large timing belt drive (4 leadscrews driven by 1 step motor), whole system is accurate to +/-0.0005" with up to 600lbs on it
cog belts work awesome for high precision/high torque applications, just make sure you do your math right and line everything up, and keep at least a few teeth engaged in each pulley to prevent skipping teeth.
if any ?'s hit me up.
-Q