Been out for years.
Look at it from a logical perspective. XADO claims it creates a ceramic layer over worn metal. And somehow, this is supposed to happen in an engine with pistons moving at 600 - 6000 rpm.
This is ceramic coating. Requires even application and oven curing with no other contaminants coming between the metal and the coating.
This is what happens when you let it build on its own:
Okay, so that's a shameless exaggeration. The more mundane truth is that the ceramic additive will polish your bearings and probably make them smoother (imagine it as sand-blasting your engine internals), but they won't build up a permanent layer. If you have any small leaks, it will sometimes build up where those leaks are and seal them (much like sediment builds up where water "leaks" out of your shower head), but a lot of times, it won't. Reviews for XADO are mixed.
Personally, get a better motor oil or something with zinc, which helps prolong bearing life.