They seem to perform as promised. I helped install one.
Once the sub base is level, the pad itself is pretty easy to put in. So far, with 2 Minnesota winters, the pad is in good condition, and show no signs of wear.
It's made by the same company that makes the Rhino Liner spray in truck bed liner, which is a quality product.
Since the pad is specifically made to suppost spas, I'd think that the pads ability to support the weight is a non issue.
Brewman