Stiff and expensive.
Other than that they will probably last a long time. When they say "Ironman" shocks and springs they aren't kidding! A friend has them in his '78 and hes gettin ready to take 2 leafs off. Its been several years and they aren't breaking in. My Skyjackers rode softer immediatly after the install.
Might want to look into pnuematic "air ride" seats along with Bence and his OME lift