Maintenance is certainly important. I purchased it used off of Craigslist at over 300k miles and I saw many cases of neglect so I figured I would try it. There are enough online reviews to convince me that at the very least, it would be safe. For every 100 people that say these types of products don't work, you'll have 100 that swear by them.
As another example, if I posted about undercoating, some say it's good, some says it causes more problems than it solves as it traps corrosive elements. I still meticulously undercoat my vehicles and, in the case of the 4Runner, have spent many hours sanding and using Rust acids to clean and then coating the underside.