I second what Forrest said.
I will use a cover religiously when away from home. I have both a Noah and a Weathershield: The Noah for weight and ding protection, the Weathershield for rain repellancy. Plus, its machine washable at home

(Also got the car jacket for my Sunday driver

)
In high winds I just attach a long bungee cord through the loops in the cover and "lasso" it through underneath the car. Never had any problems with wind pushing the cover up since the covers are custom made for the car.
Definitely must dust and qd very throughly before using the cover. It can take me 1/2 hr some times.
I will never do without a cover. A cover saved a car I had from a wild cat(?).
Here is cheapest place I've found covers, I have ordered 4 from them with excellent service. The covers come shipped directly from the Covercraft factory:
http://www.websweeper.com