"They've had adaptive cruise control for a long time now that will slow you down so that you don't rear-end anyone in front of you. In theory, you can set it at your favorite speed, and then ignore the foot pedals until you reach your exit. I haven't used it, so I don't know if it handles stop-and-go traffic jams or things like that."
I have a 2014 CLA and it works. I have gotten on a freeway, set it to 80 and never touched the pedals for over 50 miles.
As far as what it won't handle, my car won't handle extreme braking, getting cut off badly or a car that is stopped completely (doesn't see it at all). Other than that, even in slow and go driving it works perfectly (if it stops completely you have to tap the gas to go again).
Overstock is now keeping 10% of their bitcoin sales in bitcoin: