They do work for people who will be riding tires until they are falling apart. I have rode tires where I could see Mr Tuffy through the gashes. Are you that stupid and cheap, then buy Mr tuffy like meeeee.

There may be a problem with holes where the tube hits the strip, I am not sure if it is the strip, the installation, or bits of glass making it through the tire (in my case very worn) and traveling around the strip to the tube.

In theory they add mass exactly where you do not want it, on the outside of the rim (read up angular momentum). On the other from your posting I assume the "Tour de France" is not what you are up to.

If you are getting a lot of flats:
1) Inspect your tires every 3-5 mi and pick out the glass.
2) match the hole in the tube to the place on the tire above it. Check that area very carefully, you might have something tiny like a mini staple embedded there.