Those stop systems are becoming very popular. As far as I know, all the major manufacturers are offering them now (Powermatic, Delta, others).
I think it's a great idea, but for 2 issues:
1. Depending on the mechanism, I've heard some of them can only be used once, then the mechanism must be changed out ($$).
2. They work by measuring resistance. If you're working with wet wood (even "fresh" pressure treated lumber), I've heard it can set off the mechanism.
I don't own one (table saws scare me to death), but that's what I've heard about them. A friend just bought a table saw and did all sorts of research on them.
Ryan