There are a lot of people using the script at this point. Most of those that are familiar with the rigging process and what this script does will perhaps agree that it is worth the cost. You can find some testimonials earlier in this thread.
I’ve already published five updates for it. Currently working on the next.
The purchase link is on Uefy 2 – Rakiz Random Rambling
As for the FastSpring platform it has been around for years does what it’s supposed to do well enough.