I tested a couple of these tables since i was a teenager because they always somehow impressed me and I like many of them and the idea in general But!
Knowing a bit more now about our body, pain, energy etc. I came to following conclusion:
Inversion of our body can be beneficial if an alignment (therapy or self help) was done first, the hip joints are in their proper place and stabilized in this position and also the knee and ancle joints are aligned and strong. And this takes about two month of therapy and/or self help alignment before an inversion should be done.
An alternative during this two month is the exercise between two chairs for example as featured in my website, this is not stressing the lower limb joints.
Blessings
Thomas