I think for me being impressed may be more closely coupled to approval than most people. I wanted to express my disapproval but I didn't think I could do it in a way that wouldn't degenerate into a personal attack. So, my intent was not particularly clear. Sorry.
From a technical perspective, I guess I'm impressed by the fact that he was able to marshal together the resources, time, and support necessary to make this happen. He's done similar stunts without killing anyone, so I'm somewhat impressed by his driving skills (although there's also the advanced safety technologies in his car, as well as the intrinsic chance you'll find yourself in a situation that could result in an accident). His endurance is also admirable - it must have been very difficult racing the clock for hours on end while maintaining extreme concentration. But then, there are also people who drive drunk, drive while distracted, or drive dangerously badly-maintained vehicles regularly, and nothing happens to them, so I guess that makes the 'reckless driving' aspect slightly less impressive.
Does it count if my level of impressedness is fairly low? It's not 100% uninteresting, but it doesn't seem like a particularly amazing feat, either. I can believe that if you disregarded laws and drove fast, with some planning, you could do this, so the result is roughly what I would've expected. It requires some execution, but it doesn't give me the "wow! that's really possible?!" kind of awed feeling.
I don't find it plausible that anyone could not be impressed by this, though of course approval of this is going to be spotty.