The 2 big issues that are not intuitive from early use, but can really bite you:
1) Crests: The system will lose track of the road edges on even moderate crests. The system won't make lots of noise indicating it is in over it's head...it will just do its best. Often that means a final desperate steering action to the right or left...if there is oncoming traffic, you won't get a chance to respond. You need to anticipate the issue and if there is any chance of crests on the road being used, don't plan to use the system...except as an experiment to understand it's limitations.
2) Speed-limited Autosteer: The system has an oversight which I expect will be patched in the future. It is a result of the previous patch of autosteer speed limited to 5mph over local speed limit on certain roads (usually non-divided highway). Let's say you are travelling along in a 65mph zone with the Autopilot on and set to 70mph. All is well. Now you enter a 45mph zone...and the car will slow to 50mph (5 over). Now let's say you see some road debris, and decide to steer the car to avoid it. The steering input will cancel Autosteer, BUT TACC will remain active...and it is still set to 70mph. The car will suddenly accelerate. In the wrong circumstances, this can result in bad news.