anyone with experience of the "CD lathe"

I've been using one for the past few months, and all I can say is, I can't imagine myself doing without it. The link below will take you to reviews on the Audio Desk Systeme website -- I took the plunge after reading Richard Foster's review in HiFi+, and I've found his comments to be completely accurate.

http://www.audiodesksysteme.de/index.php?kat=10_23

The operating principle seems sound

Why? The principal physics of operating principle is claimed to be similar to the well known green felt tip pen scam? The description claims that "Light scatter is often to blame for poor sound potential. Light scatter moves randomly through CDs and audibly deteriorates reproduction." I have not read anything like this in AES papers...surely manufacturers would try to deal with this problem if it were real.

Yes, and the improvements to the quality of music reproduction is significant. I do not need to know all the physics. This tool is the real deal. My problem is finding the time to cut the cds.