Bought one once for our Class A. After struggling to get it on top of the roof, catching my breath, hefted it back down the ladder and returned it to Camping World. Too much work, hazardous, expensive, and it just doesn't stay parked long enough to make it all worth while.
Did use one on our truck camper when we lived in snow country. Light, easy to spread and tie down, helped to contain heat. And cheap. Made a good hide out.
For a younger person, in snow country where it stays parked for months, and on a Class C I think it makes good sense.
2011 Jayco Greyhawk 31DS with wife & 2 dogs
06 Jeep Grand Cherokee LTD