Originally Posted by Griz
This comment is now 6 months old, but...
Debatable. I would never put a cover over a car unless it was freshly washed. Otherwise, as you put it on and remove, it's going to drag that fresh coat of dust across your paint and create hairline scratches.
My M3 is SilverStone II and I drive the car everyday. I park in the California sun under a "nest" of very large eucalyptus trees. The fallout from the trees and damage from the sun is a much greater problem than the minor scratches that the cover might create. Additionally there are times when there is some autobody activity (sanding and painting) in my Automotive Technology lab.
I was sorry after 13 years with my Arvus Blue E36 M3 that I didn't use a cover. The tree branches, student backpack, paint over spray, and the sun took it's toll.
Short of the "glass case" the cover has worked great for 16 months. My 8 minute drive to school on a well maintained road does not add much dust to the paint.