I have both the MiNewt 600 and 150 cordless. The 400 and 100 modes respectively are what I usually used. I don't put them on flash very often except around dusk or dawn where I can see good enough but maybe the car drivers can't.
As far as too bright, I was doing a 24-hour road race a few years ago and notice that I could see my shadow in the middle of the night. The guy was still about a quarter mile behind me! He had some fancy HID lights - 4 bulbs I think - and oncoming cars were flashing their high beams in an attempt to get him to lower his lights. They were bright!