I just gave HFDA a decent tryout--45 miles of Interstate each way. On the way up--driving in daylight with sunglasses one--it performed really well. On the way back, driving in the dark, I kept getting the "pay attention" nag over and over and over--sometimes to the point of the car telling me to take over. Keep in mind that I hadn't changed my driving position or seat position at all. Perhaps I was slouching a bit because it was later in the evening and I was tired, so I tried sitting up, and lowering the steering wheel. None of it seemed to help. Maybe it was due to it being dark outside? I don't know, but it was honestly disappointing, because driving at night is a time when I would really wand HFDA to work.