I have used a cover constantly for the last twenty years on all my cars. The naysayers are correct if one uses teh covers carelessly. To use them properly is a PITA, but necessary if you want to avoid paint damage,
1. clean the car prior to putting on cover, every time. Even once without can scratch paint.
2. wipe down the cover before removing it, every time.
3. if you can afford it, pay for protective film for the whole car. That will make cleaning the car easier, help protect against damage from the car cover, sap and almost everything else. That single thing will also make the placement and removal of the cover easier (the film is slippery), and the cleaning becomes nearly trivial.
Those three steps, PITA, though they may be, has made all my cars look new when they were old. My spouse had a BMW for ten years that looked showroom fresh thanks to protective film, although that one had film replacement after the first five years.
When your car must live outside under trees, nothing will help as much as protective film, including the cover.
FWIW, when I drove exotics the covers were invaluable to establish a bit of anonymity. If you need that, ensure you do not buy a logo cover, which defeats that purpose.
