Add me to the list of people who have no issues with it. I have to say, it does seem overly conservative to not even engage a feature for fear that it won't work perfectly. Keep in mind, you're not abdicating all responsibility to the car, with no way to take control.
Case in point, an 18 wheeler departed from it's lane just as we were overtaking it while using Drive Assist. I grabbed the wheel and aggressively steered to the far left of my lane and slightly onto the shoulder, which, presumably, disconnect Drive Assist (I didn't give it a shred of thought). Simultaneously, I hammered down the throttle to get outta here.
Rest assured, if you don't like what you're seeing, disengaging is trivial. Tap the break, turn the wheel hard, or disengage it through either of the two buttons on the lower left of the wheel.
It seems odd to not test out a feature for fear that it won't work perfectly. Hopefully this will encourage you to give it a try and form your own opinion about its operation.