I used it on my 94 Suburban. It had 145,000 miles on it, and I FELT it gained power, but there'* no way to know for sure, because I didn't do a compression check. From what I understand, it is supposed to be the only product that actually works, but it, like all band-aids, doesn't last. It'* something you're going to have to do every other oil change or so, because it wears off the cylinder walls over time.
One thing I was always nervous about was the fact that this stuff is designed to fill little scratches and cracks in the cylinder walls. Whaddya think it does to the media inside your oil filter?