Well, airmatic has been standard on the S-class (although they don't use exactly the same components) for quite some time and has been standard on some E-class models. Better knock on wood but I haven't had problems with either of the two cars with Airmatic suspension. And my car has seen harsh conditions. I would assume first problems having been ironed out.
Ride is not like on typical American cars, at slow speeds one may expect something like for trucks with air suspension (comparing the smoothness to trucks without air suspension) but that is not the case. At higher speed you feel the difference, unless you want to use the "sports" mode. The option to raise or lower the car is also handy (odd that they removed the option to lower the car on a W221, I've understood that it only does it at reasonably high speeds, automatically).
If you look at all the components that are different, it should be obvious that retrofit is not reasonable.