I have a can of this. I bought it at a local air festival for about $8 a can (I think.)
Anyway, it does little on already yellowed plastics, but I have sprayed it on non-yellowed plastics (Amiga and Commodore) stuff and will await the results as well.
BTW, I just found a small treasure trove of Amiga equipment. The guy had about a dozen A500s, two A2000s, a bunch of A500HD8+, a couple of Trump Cards (I'm looking forward to playing with these,) two A600s, and an A1200.
Here's the catch, they were all stored in a metal shed. Most of it is HEAVILY yellowed. Based on this, I would assume that perhaps extreme heat (in excess of 100F in a metal shed in Florida) and oxygen alone is enough to cause yellowing.
