The thing with these markers is, when a cd player has trouble reading the data stream on a cd, there's no time to go back and re-read what it missed like EAC does. This is real-time, the song has to keep going, so most cd players just do the best they can. If they miss some info, so what. Interpret what you've got and move on. So the markers are supposed to I guess make the discs more reflective, or somehow make it easier for the cd player to read what's on the disc. That way more of what you hear is what was actually recorded on the disc, instead of the cd player's best guess at what was on the cd.

I've never really tried them. I have no idea whether they make any real difference at all. If the above explanation is correct, I would imagine that if they do work at all it would be with lower quality cd players that seem to have a real problem reading lots of discs.

Also no idea what they would do to a laserdisc. Again I would imagine a more across-the-board benefit would be seen by buying a better laserdisc player instead of a magic marker.