There are testimonials on their web site: people get cuts, but only slight ones. I can understand if the inventor doesn't want one!
They sell the replacement parts for around $60, and the system doesn't trash the entire saw.
The other interesting thing is that they don't sell it as an aftermarket add-on. It's only available on their premium line of table saws. That'll be at least partly for reasons of quality control, but the saws themselves do look rather nice though - I don't think they've skimped on quality there.
The other system (with a detector blade guard) I've looked at too. It's not on the market yet, but has patents pending. The stopping system is electric (seems from the patent to be straightforward if heavy duty DC injection braking, but I may be wrong). I'd be surprised if it is ever launched commercially, for a number of reasons, some technical, some marketing strategy.
The SawStop one looks completely thought through, the other one doesn't. I'm not sure if I'd want one, but it's certainly clever.
E.