The Hamiltons cover is fleece lined with some special breathing holes etc - fully waterproof and does not scratch the paint work.
I have used it for a couple of years now and my motor is always kept polished and clean. My self and other friends + members of the car trade (with a lot more expensive motors than mine) - swear by these covers.
Basically my motor is pretty much kept immaculate and stays that way when covered. no scratches, no marks, no water gets through. Its tied with plastic clips around the middle but ive added para chord ties to the 4 corners. it hasn't ever blown off, and thats through some serious winds which have taken out the garden fence!
just sayin' - might help someone decide.