I think they are a good thing. How many times have you heard, after a motorcycle accident that the cage driver "Just didn't see the motorcycle"?
The vast majority of drivers are not looking for motorcycles and tend to look right through them. The more you make yourself visible the better.
I had both on my VN800 and took them off to transfer to the new bike. I will do that in the next few days.
The only time I knew of any reaction to the headlight flashing was on a country road some teens, or a bit older, were coming toward me on a two lane pretty fast (read speeding). I saw them slow down and when we passed they realized I wasn't a cop and made some kind of noise or gestures. No big deal. I just kept going at about 55 and never saw them again.
I am pretty sure drivers see the light flasing and don't quite know what to make of it. But they see it.
As for the brakelights. My old bike had two bulbs back there, but the new one has only one. I have no idea what Kawasaki is thinking on that. Costs? Anyway, in the bright sun out here I think the flashing brakelight is going to be more noticed.
I personally don't give a crap what others think, as long as they see me. Better to piss off a few folks or have some think "you ain't cool" than be dead or maimed.
Just my humble opinion.