I think lighting enough to be seen by is adequate where there is street lighting, take for example a Cateye EL-530 or two. I can't see the point in lights that are painfully bright. I've seen a few oncoming cyclists (at night) with them angled to highly - and they are not only a nuisance to motorists, they are a nuisance to other cyclists too!
If your average moton doesn't see an EL-530, all anything super-bright and death ray like is going to do is dazzle or panic them, possibly resulting in erratic or unpredictable driving. Or, if the motorist is so minded, give them something to drive at.
Don't get me wrong, on an unlit road, I'm all for having something brighter to see by.