I got a Fenix light and "twofish" clamp for my bikes that don't have the dynamo that's on my regular commuter. It is super-duper bright, so yes, I aim it down.
I took it out with me the night it arrived 'cause I had an errand that meant a mile or two out in the country. Oh, my, did it come in handy. Three times cars came at me with *their* brights - and usually I have to pull off as they approach. I just "flicked my brights" - just a wave in their general direction, from half a mile away - and the lights dimmed right away for 2/3... took three flicks for the third. (I do *not* want a blind driver aimed at me so I'd have pulled off anyway, not tried again as it got close...)