In all honesty the idea is that you would use it once the engine had significant wear and age on it to improve the seal between the piston rings and the cylinder walls. It supossedly bonds to the metal sealing up scratches and imperfections in the metal to improve compression and reduce friction (same idea as that Z-Max stuff, only much cheaper).
However, today's oils have many additives which basically do the same thing. This product may do it a little better, but I doubt that it is enough to really notice a difference. Maybe under certain conditions it would help, but I don't think it is really necessary to ever use it.
The only personal experience I have with it was putting it in my sister's Geo Metro several years ago. Her car was getting old and worn and I got a bottle practically free (I worked at Advance Auto Parts and they had a damaged bottle) so I tried it. I didn't take any scientific mesurements or anything, but here car didn't seem to run any different, and certainly didn't have any more power. If it did anything it wasn't noticeable. My $.02