I've found them very useful for lifting washing machines and freezers up to adjust their legs. I think one of the main things they are designed for is fitting window frames, if you have a few of them (the bags that is).

I've also found them useful for lifting heavy doors up so you can get the hinge in line with the screw holes and I had a baby gate that needed taking apart and an airbag was the only way I could exert enough force on it without damaging it.

One day I might find a child with their head stuck in some railings and they'd be useful then too!