I bought a couple in Sturgis in 2001. Anytime we head out on a ride that's more than a couple hundred miles, they come along with us! They make ahuge diffenrece when you're going on long trips. I do not use them for normanl rides though...
I used velcro under the seat to hold the cover. You do have to take the seat off to adjust the air- one screw and undo the velcro. I only had to adjust it a couple of times. When it sits out in the sun, the air will expand.
Wow - I love that idea Locknut - Nicely done! - Grayhawk to me it seems they all run around the same price vs. size - You might get lucky on ebay but for the most part I have not seen a real big difference in price.