All of my vehicles are black. I have used it and I love it. Easy to work, great shine, and it does not stain trim. It does streak windows so be cautious around the glass.
Perhaps the others that haven't had luck with it live in an area that is more extreme in environment (desert, high Sun UV exposure, etc). I live in south central Pennsylvania. This winter will be the first in using it so I'll be interested to see how it holds as it typically is the harshest season here.
Is everyone following the directions to the letter I wonder...? Keep in mind that there is the wax and then the touch up spray....