If I have my car outdoors for any reason overnight, this is the cover I use.
Very nice, and it is almost completely waterproof. Has a lifetime warranty also. It drizzled one day, and not a drop touched the paint. It fits perfect, and is very tight. It also comes with straps front and back you can use to prevent it from going anywhere in high wind. I never used them becuase it fits really snug. Never had any problems with scratches. I just put it on the car inside out on occasion, and wash it off before washing my car. Very easy.
For indoor storage, I bought a car blanket. Much easier than dealing with the cover, and I can have it dry cleaned if I need to. Just throw it on, and that is all.
This site has good comparisons on a lot of different covers out there, and they ship very quickly.