The SawStop works on electrical sensing. Your fingers and hot dogs send an immediate electrical conduction and the brake kicks in. A very fast action that touches the blade could result in a nick but that's about it, electricity is faster than you. The early SawStops had issues with green lumber kicking off the brake and metal objects, like foil covered sheet goods can still cause a trip. The main issue with SawStop is that it's a mechanical devise and it can be shut off. Mechanical devises are never 100% dependable. They don't work at all if turned off. If you run dado blades, you need to install a special cartridge. At this time, I'm not aware of a cartridge designed for molding heads. The cartridges are one time use, if they fire off, you need to buy a replacement in the $90 range. There may be damage to the blade that the brake engages. Haven't heard anything about damage to arbor bearings from the abrupt stop but most folks aren't going to be firing off the cartridges very often. All the safety issues regarding saw use still should be followed. The device will not prevent kick backs, debris flying at you or electrical shock.
Mr. Gass invented the braking system and tried to sell it to the saw manufacturers. They were not interested. It wasn't something that could be added to existing designs and would require a complete new design and tooling. He may have wanted too much money for his patent. In industry, OSHA has standards that apply to table saws which include guards, anti-kick back devises and most importantly, proper training of personnel. When he couldn't get the manufacturers to buy his technology, he lobbied to have it become a required standard for saws. He was not successful. Gass decided he would make his own saws. They are a top quality saw and the equal of the offerings of other cabinet saws on the market but they are the only ones with this braking system. Sort of like an air bag in your car. You never want to have to use it, it's expensive if it goes off but you might be real happy it's there if ever needed.
DIYers are on their own, not that some in industry aren't as well. There are a lot of businesses that don't follow OSHA standards, although, they are required by law. If a person is properly trained in saw operation, there should be no reason for their hands to be anywhere near a spinning blade. If guards are in place it would be difficult to contact the blade. If you follow the safety rules, there is no way you would slip or be performing any action that could bring your hands near the blade guard, let alone the blade. The problem is that many people using saws don't know or follow the rules. People don't regularly die from table saw injuries. If they did, things would be different. No safety devise is going to protect you from yourself.
If you want a very nice new saw and don't mind paying extra for the safety brake, the SawStop may be for you. Just because you have air bags in your car doesn't mean you can drive recklessly. Same with the SawStop. You hope the bag goes off if needed or the SawStop brake engages but it's not 100% guaranteed. I think it's a great addition to safety, just the same. Even under the best training, people are going to make mistakes and learning often takes place the hard way. It doesn't matter how many times you tell someone not to touch the burner on the stove, eventually, often accidentally, everyone learns it for themselves. I don't recommend learning the hard way on a saw. The cost can be a lot more than the cost of a SawStop.