I put one of the green ones on my down tube. It's not crazy bright, but it's noticeable enough that cars seem to be giving me more space on my morning commute, and noticeable enough that some strangers in a pickup stopped to take pictures of me. It's lasted through a wet day where the front wheel through a lot of wet road gunk all over it, but I haven't really put it through its wet weather paces yet, so it's hard to say whether or not it'll survive multiple downpours.
My last recharge I got about ten to fifteen 12 mile rides with it on steady mode.
For about twenty bucks, I recommend them.