I've had so many opportunities to try this over the last few months.  When I visit friends who have one I always say I'm going to try it, but then get distracted by other things.
 When I went to visit my friend E, her dad has one in the basement (that I have been meaning to try every other time I've visited).  I finally remembered to do it!
It felt good and stretched my back, but I could only hang for 20-30 second at a time cause it was difficult for my feet to stay supported in the straps.  Next time I'll try it with my shoes on!