Yes, i use the green marker and the improvements are audible to anyone who can hear. I wouldn't bother if it didn't work. I asume that cleaning the edge of a cd would help as well. By cleaning i mean shaving. i have seen an expensive device that uses a blade to shave a thin layer off of the outside edge. Have you ever looked closely at the edge of a cd. When you do this remember that a cd works by reflecting a beam of light. Hey, this isn't rocket science. But, one important thing, don't spend $20 on an edge treatment, you can buy the same thing at any art store for $3. It is a Lumacolor pen, I forget the manufacturer but the guy or gal at the counter will know what you are asking for. Best thing is that this approach is permanent and one marker will treat thousands of cds. Try it but, only if you have an open mind. A biase on the front end never produces a desirable result. My determinations are based on a blind listening test that i preformed. I had two copies of the same cd , one of Sam Mclains, you know which one, I treated one and left the other alone. Then I did what sooooooo many people dont do, I listened, not knowing which i was listening to. I am now and was then a believer.
If you are going to form an opinion of something form it based on experience if possible. And, for three dollars no one has any excuses in this case.
Oh, one other thing, the result is directly proportional to the quality of your equipment. This is a subtle result but deffinitely noticable.