I have a Smart Lunar R2 and find it ideal. Mine is the old 2xAAA version and the batteries last for ages, I think it might still be on the original set. It is very visible (also bright, but bright doesn't always mean visible) and lightweight. It also comes with a seat stay mount so it doesn't have to go on the seat post to be obscured by coats, bags, flabby arses etc- that is a particular advantage on retro road bikes because they tend to have quite a short seat post.
I've just bought the new rechargeable version for a second bike but I've not used it yet so can't comment on battery life, but if anything it's even brighter than the old one.