Short answer: DO IT, you won't regret it.

I think the flicker issue has been addressed - I've noted the same thing - flicker at a slow walk, nothing beyond that.

I have an Alfine dynohub with a Supernova E3 Pro headlight and tail light. I've used both the symmetrical and asymmetric (German DOT compliant) models. The symmetrical throws a brighter, narrower beam farther down the road at the expense of broad lighting from 0-25 feet. The asymmetric is not quite as bright, but provides a phenomenal "carpet of light" from the front wheel to about 50 feet out, then rapidly dissipates farther out.