SCC works well at highway speeds on long stretches. On curved roads, I have occasionally experienced it mis-calculating what it thinks is a car ahead when they are really in the other lane, but for the most part it works good on curves. It doesn't work so well in congested/slow traffic for a few reasons.
#1 - In slow traffic conditions, in many cases the response time isn't quick enough to detect a car ahead that changes into your lane. The SCC does not react quickly enough to slow down and avoid a collision with the car ahead. I assume the emergency breaking would kick in to avoid a collision but I'm not that brave.
#2 - The SCC sets an upper limit to the speed. For example, in slow traffic, you might have it set to 20mph. Then when the traffic flow momentarily goes to 30 or 35, unless you want to continue going 20mph and slow down everyone, your forced to manually re-set the upper limit by adjusting the cruise toggle switch. This is an annoyance. I find myself having to re-adjust the upper limit up and down to coordinate with the surrounding traffic flow. SCC should auto adjust to the surrounding traffic speed on its own.
#3 - In heavily congested traffic, the start/stop feature disables after 6 seconds at full stop. This is super annoying to have to re-engage the SCC so many times in stop and go traffic. The whole point of it is so you don't have to hassle with it. Out of the 3 issues this is probably my biggest annoyance.
Hopefully Genesis takes notes of this and upgrades its software.