cyccommute, it's true that dyno lights can and do fail. The failure rate is less. Less than an admittedly low failure rate of battery lights. The difference is significant for me but not for you. Similarly, the difference in cost is significant for you but not for me. We are weighing our parameters differently.

I would not suggest a dyno system on every bike to a person who frequently rides many bikes. My racing bike, which I use on long, fun rides, often with friends, doesn't have any lights mounted to them until I take a ride, and of course, they are battery lights. One of my errand bikes has battery lights. Clearly, I find them useful and worth the money for some uses. I prefer dyno systems on my two most frequently used errand bikes. So I'm not a purist. My point is that dyno lights have some advantages, so it's a good choice for some of us, some of the time. The light provided is completely adequate, the price is reasonable (and that's an opinion), and the convenience is great.

I hope I've put this stuff in a way that you can agree with or respect. I don't mean to attack your views at all. I think mine are stout enough not to need to be attacked, either.