As Paul Harvey would say, "Here is the rest of the story".
Saw Stop is a great idea! Invented by a lawyer who has patented it. I believe he offered it to the major manufacturers and was turned down before he started his own table saw company. The manufacturers stated it was to expensive and not worth the extra investment. (A friend with a small cabinet shop had an accident occur to an employee recently. The medical bills were well over $40,000 as compared to a $3000 Saw Stop table saw.)
Fast forward a couple of years...A man was using a small job site table saw to cut with, he removed the fence and the guard and promptly cut himself severely. He filed a law suit against the table saw manufacturer for failing to make a safer saw since they were one of the ones who turned down the Saw Stop idea. He won 1.5 million for his stupidity. Now the government (CPSC) is looking into table saw safety and the result will probably be in a couple of years is that every table saw sold in the USA will have to have this type of safety built into it.
BTW The patents are so tight and well written that no one will be able to produce anything similar without infringing on the patents.
So, if you are in the market for a cabinet saw or table saw anytime within the next two to three years, buy NOW! The device will add about $1000 to $1500 top the cost of a $3000 cabinet saw taking it out of the range of most serious woodworkers. A contractors saw will have about the same cost added as well.