It's real helpful in traffic when you have it; real dangerous if you think it is there -- and it isn't. Partial versions slow you down while others bring you to a complete stop. Though Lexus brought the first system to the U.S. in 2000, many domestic models didn't begin offering it until a decade later.
Some of these new cars are already scheduled for earlier-than-usual facelifts. The rest of them are already overdue.