I have a 21 ST with the premium tech package, and just last week I discovered the intelligent cruise control. It basically takes adaptive cruise to the next level. It uses the info provided from speed sign recognition and can adjust your speed based on that info. If you turn it on it will adjust your speed up or down to the posted speed limit, and you can tailor it to your liking such as +/-5 mph or more. I tried +15 mph and it worked. Don't know how far you can go but it will allow +15.
Say you set it for +5, while your on a side street with the speed limit of 25 mph it automatically go to 30mph, when you turn onto a street with a 35 mph it will go to 40, etc. You can also adjust up or down with the steering wheel controls just like normal cruise, but if you exceed your setpoint, it will constantly flash the cruise/ speed sign on the dash until you get back to or below your setpoint.
It comes in handy if you travel on roads that have multiple speed limit changes. But if you travel where there is a constant speed limit it is not needed.