Well when it comes to gardening outdoors, you don't need to worry about having wire cages for plants like tomatoes or green beans or anything that needs help staying off the ground. It would also keep most pests like ants and most weeds away because they're suspended in the air. From what I've been reading the only thing that could be a downside is that they can dry out faster.
Apparently it's good for anything that grows as a vine, where you can hang the roots wherever and then the vine just hangs below... I wonder if I try planting passionflower upside down if it would work...