Ok, i don't know a lot about airbags, but from what i have learned, Dags is on the money. A mate is running a Holden front, Jag rear with bags in a Dentside and has no springs and has never had an issue. (it is a show truck though)
As for the springs, i took the 'overload' leaf and the next smallest out and it made it soft enough to ride the bumps but still stiff enough to handle corners.(with sway bars etc.)
The down side is that i can't carry much weight before it hits the bump stops, but i think if you run more pressure in the bags when you have a load it would fix this.
As for the axle tramp, if the tyres/road/track get very sticky, mine can start to axle tramp.(not often). This is an easy fix with a set of tramp rods, when i get of my but.
Hope this helps.

Chris