I used it on white and silver cars for about eight years; never had a complaint. I don't use it on darker coloured cars now.
A couple of observations:
1. As BlueLibby points out, grit is the enemy. I only used mine as a first pass right after the wash. I did not use it to scrape off every last drop of water. Don't put it down on pavement; wipe with a towel after each pass.
2. The silicone can/will harden over time. Keep it out of sunlight and wipe dry after every use.