I bought one to cure a whineing from the rear of my Hinkley, it seemed to cure the problem, but i have had the seat rebuilt with better shaped padding and better cover material.
However when I took the Hinkley to a rally in Portree last year I used the air hawk and splash/ dashed 610 miles each way, with no problems. I changed the amount of air in it every couple of hours, just to spread the load, it needs very little air, too much and you would be sliding about. I did get the expensive one, although I can't remember why, mine is the pillion version but it fits the front fine. for the use I get out of it I dont know if I would replace it, but if you were going to do loads of miles it would be worth it, but a lot of people swear by a sheep skin.
JimR