Even though my car is a 6sp manual, the automatic distance keeping is making the commute much more relaxing. I can't recommend it enough.
Funnily enough the radar system is separate to the AEB, which uses cameras. AEB stands for automatic / autonomous emergency braking.
As I'm someone who likes to know how stuff works, especially in cars for familiarity should a real event occur, I did set out to experience how AEB works. I rigged some large but light cardboard boxes, reversed down the road a bit, accelerated quickly to around 40 km/h, kept the throttle pedal steady as though if to drive through them.
All times, although it felt like surely it wouldn't, the car intervened at the very last second. The first time it drove through them by a metre. The next two times the car stopped before impact. System uses 100% brake force engaging the ABS and also putting on the hazard lights for good measure.
I came out highly impressed. It ought to pick up cars better, but I'm not about to actively try that.
BMW's anti-collision system is on even during manual driving.[1] BMW will brake even if the driver is pressing the accelerator. So will Volvo. Top Gear compares the various systems as of 2015.[2] Volvo did best; Mercedes didn't stop soon enough and hit the dummy car. VW's city car only does this up to 18MPH.
Maybe Tesla has a false-alarm problem that BMW and Volvo have overcome.
More to the point, this behavior needs to be standardized, or people shifting from one car to another will do the wrong thing. The National Transportation Safety Board is working on this.[3] In a few years, anti-collision may be as standard as anti-skid is now.
[1] http://www.theverge.com/2015/1/5/7494989/bmw-i3-self-parking... [2] https://www.youtube.com/watch?v=PzHM6PVTjXo [3] http://www.ntsb.gov/safety/safety-recs/recletters/H-15-008-0...