I have two lights in front. One dynamo powered light and a battery powered 850 lumen light on my helmet. Works great. I can turn my head in any direction to light up any area. The helmet mounted light also lets me shine the lights toward oncoming cars when I need get across the road at bike crossing or crosswalk - 850 lumens seems to let them know I'm there.

Most of my commute is on an MUP. It's in the trees and can be very dark so the helmet light really lights things up. However, oncoming cyclists or walkers can be blinded and annoyed by such a bright light. I can easily reach up pivot the light to shine to my right side and out of the eyes of oncoming riders or walkers. The dynamo powered light shines it's beam low to the ground and has a distinctive cutoff to keep the beam out of the eyes of those coming towards me.

The only problem I find with the two light system occurs in fog, mist, or rain. The helmet mounted light is up too high and you actually get the light reflecting back at you in those conditions... it's actually a hindrance to seeing the road. In those conditions, I just turn it off, slow down, and use the dynamo powered light to guide my way.