I've used an air caddy a couple of times. There are a couple of advantages and disadvantages. On the plus side, you don't have to take off the pedals, derailleur, rear wheel off or the handlebar (unless you have straight bars). While you probably would have to take the panniers off, there is alot of room in the triangular box to ship stuff with your bike. You could certainly ship your panniers and other gear with your bike. I put a mountain bike, farfarer trailer, helmet, shoes, handlebar bag and camping gear in the box last time I used it. You lock in the front fork dropouts, which protects the fork. The rear wheel is wedged into into the small angle on the box. Never had a problem with in the times I used it.
On the minus side, it is larger than a standard bike shipping case so it costs more to ship it. The cardboard box is pretty sturdy but I'd say three out and back trips is max unless you duct tape the whole thing. You also need a place to store it once you unload it.