I have a WeatherShield cover and to be honest I was disappointed in it. It is NOT as waterproof as they say, with a moderate rain fall I sometimes get water under the cover.
One of good points though is that it's very light, so it's easy to carry and store.
I got my cover for a rather large car (Lincoln Town Car) and it costs me almost $400, so for that kind of $$$ I think it should do a better job at keeping water out. One of our fellow Senior Autopians, Darbh, also has this same cover and was not totally happy with it considering what it cost.
Sorry if it sound like I am dumping on the WeatherShield, I just want to be honest.