I've had them, used them and ditched them. I just don't like the drag on the bike.
If you are using it to be period correct, make sure you have a real light available if needed. Such as really dark areas, traffic and etc.

I live in a community where I ride regularly at night. The way people drive here, you need all the light you can put on the bike. Anything less would be suicidal. A generator just won't hack it.