I’ve got one, I’ve found that sometimes it helps, sometimes it doesn’t.
Personally my back is giving me grief sporadically at the moment (sciatica, lower back pain) and this it doesn’t seem to help with, in the past it has helped quite significantly when I’ve also had sciatica and back pain. The pain is different now, just in the same areas.
So, it seems to be a bit of “suck it and see”. It may help you, it may not.
One thing to note is that I notice how much strain it puts on your knees, ankles and hips with all that stretching, especially with full inversion.