I just used Turtle Wax's BlackBox products this morning on my wife's 2003 Nissan Altima's (affectionately named the "mommy" mobile) neglected black finish. I must say that it does work. There were several scratches all over the trunk area of her car as if a cat(s) had been walking across daily. The scratches varied in length and depth, many of them revealing the white or primer? underneath. A proper application of the products significantly minimized the visibility of the damage. Many seemed almost invisible. We were both impressed. Will it last? Only time will tell as this is the first time that I've used it.
Just so you know as a benchmark, I also have a black 1997 Mercedes SL500 and a black 1987 Porsche 944 S. Both of these vehicles I keep in as best condition as possible. Both vehicles are Dawn washed, claybarred, Zaino'ed with several coats of Z2 and accelerator twice a year (Spring & Fall). Frequent maintenance in between consist of car wash soap and a carnuba layer of P21S to give the protection the appearance of "depth and wet" in addition to the shine.
My wife prefers to have nature do the washing of her car and considers rain as a sufficient cleaning.
To impress me takes alot since I have tried most all of the products claiming to give that showroom shine. But a rescue of the mommy mobile's finish sold me.