It's a great addition. It doesn't rattle at all. You will notice a slight increase in vibration compared to the stock mirror but it's not too crazy and you'll stop noticing it after a few days. Absolutely no noise is produced from the vibration increase.
You install the auto-dimming mirror onto the existing mirror mount on the windshield. The base of the mirror "floats" on the upper-center of the windshield (as you probably know). You re-use it for the install. After removing the standard mirror, you swap the standard spring/clip in the base with the stronger one that is supplied with the attachment kit. I'm guessing some people are forgetting to do and is why they are experiencing rattles after installing the auto-dimming mirror.
