any + experience with CD disc modification ?

anyone have evidence or blind testing positive experience with disc modifying tweaks like black markers and machines that true the disc to reduce vibration?
FWIW - I've blind tested the following tweaks with several friends and my spouse: Herbies Black Dots, freezing disks, Walker Ultra Vivid, Olde English spray polish. All listeners have noticed a difference between treated and untreated disks of the same recordings; differences we all consider positive. i.e. the listeners invariably liked the tweaked disks as do I. Incidently, I prefer the Olde English to the Walker for treating the disks. And, it's a lot cheaper - about $4 at Ace Hardware - vs $75. for the Walker Ultra Vivid.
I've also tried the green edge treatment and none of us could hear a difference.
I have used the CD stoplight pens for years. This is the green pen that treats the edge of the cd to prevent light reflections within the player......

I usually buy them 2 for $35 from Music Direct and one pen will treat over 200 cds or dvds, so it ends up costing less than 10 cents per disc.

I have noticed a slight audible improvement on the same system using one treated cd and one untreated cd of the same material. Not earth shattering but an improvement.

happy listening
I have done extensive testing with many different tweeks through the years and have come to the conclusion that some work extremely well, some marginally so and some with trade-offs that are not worth the effort. Top shelf tweeks include the following:

* AudioDesk Lathe Treatment with Marker Edge
* Bedini Ultra Clarifier preferably the 4 Beam
* Densen DeMagic and/or Ayre CD (for overall system)
* Mapleshade Destat Unit
* Mapleshade Optrix (used selectively)

Beyond these there are many other system tweeks that get into bases, cones, power conditioning, etc.

I personally believe that patiently tweeking a system is indespensable to getting all the performance possible from your investment.

One tweek that I would avoid like the plague is Mapleshade Silclear. This is a product which initially provides an improvement, but then gums-up (regardless of how thin the coating) and becomes a problem downstream.
An inexpensive alternative to Stoplight CD markers is to purchase a water-based acrylic marking pen at an art supply store in your choice of colors for about $4.00. Same thing, lots cheaper.
try the millenium carbon disc, I found it worthwhile and a step up from Herbies black hole, cost a lot more though
thank to all responders.