So last night I went for my first long drive that wasn't just a loop to get through the break-in period, and I let the car do about two hours of the driving. Having now done a long drive I understand why Kia limit the feature in the US (KDM reportedly get the full autonomy features); our freeway designs confuse the UI because the lines are inconsistent, off ramps are not set up for autonomous driving so the car sometimes gets confused at the wide unmarked off-ramps, and no way am I going to trust it on a ramp or driving through tolls. I let it handle one traffic jam on its own and it does reduce stress somewhat but I am wary of the tech. It is overall impressive and doesn't "ping-pong" between the lines like Subaru's and Cadillac's systems do but does a remarkably good job of staying centered in the lane.
I still can't figure out if the version of Drive Assist actually has lane change assist; it sometimes seems to initiate lane changes when I signal, and sometimes not. I need to drive on the freeway off-peak hours and test it out under ideal conditions.