I think that there is a bit of a problem comparing mounts, in that maybe we don't know for certain how our mounts actually perform.
We might try to find out by tracking a star for example. We get data that shows the star wobbling about and immediately say "that high frequency stuff is seeing noise" - what is left after the wobbly bit is filtered out must be the mount error. But maybe part of the wobbly bit is also mount error - we simply do not know. It would not be surprising to find errors due to minor gear and bearing vibrations, or noise from dirt in the lubrication etc (1/100 the thickness of human hair will give you an arcsec of error). In principle, a direct drive mount could have lower levels of chatter if properly set up - but who knows.
Anyone know of any direct angle/rate measurements for a mount, as opposed to star position?
WRT your original question Roger, apart from ASA, quite a few high end systems use direct drive, so it clearly is worthwhile - eg:
http://planewave.com/technology/mechanical-design/
http://www.skyvision.fr/wordpress/mo...mount/?lang=en
http://www.astelco.com/html/products/ntm/ntm.htm