I don't own one, and have never used one, but I had quite a fright from one.

In the summer of '08 when I went to Colorado, I shared a hotel room with a guy from Arizona. We'd only ever emailed--never spoke or met.

I had checked-in first and was all settled in, sitting on the bed reading when this big hulk of a guy comes into the room carrying what looked for all the world like some heavy-duty BDSM equipment.

Thankfully, it was an inversion table. No whips and chains to go with the straps. Even so, I declined the offer to try it out.