I had an air-assisted suspension in both of my Mazda pickups before I traded them in. I was actually able to supplement the air ride for a bad set of leaf springs in the 1987 B2200, and you never knew there was a problem. For my B3000, I put them in to assist with towing and it made a huge difference in stability and mileage.
The problem I have is that when I had them in the B2200, I had a bag that managed to get punctured. We saw it sitting low to one side in my parents' driveway one night (the bags were set up independently). I was no problem having one go bad there, where I have access to any tool I need. My concern is what happens when I'm on the road and something like that happens. A bad spring usually give you warning, air ride may not be so kind.