Have talked with several riders over the years that swear by this product. I've not tried it yet. I've used beads and BB's that worked great on the balancing, but they don't help with the puncture proof part.
I had always been concerned that the product would eventually go to the bottom of the tire when parked for a few days, but it appears that is not the case.
The reviews on Amazon are 8% negative, which is still pretty good. Just looking at any product, youtube video, or even Revzilla reviews, it seems an average of 10% are always negative. For example, one rider claimed it didn't seal a leak, but when confronted, he didn't reply as to where the hole was. So, if it was on the outer edges or wall, it wouldn't work per the instructions.
The only thing I've seen that you really need to watch out for is that the bottle is full when it arrives. The most common complaint(of the few) was 2oz short on new bottles.
Other than that, I'd be willing to give it a go.
Edit: Doesn't work with tube tires and doesn't work if added AFTER the puncture has happened. I have used the inflatatire (spelling?) after a puncture on the road to get me to a shop.