This past weekend I just installed a Lumotec IQ Fly N Plus headlight along with a new front wheel equipped with a Shimano DH-3D71 dynamo hub on my Xtracycle. I am really impressed with the results!
The light gave way more than adequate light to see the road a good 75 feet in front of me, and lit up both sides of the two lane street I rode on. It was truly almost like being in a car or on a motorcycle. Totally safe & adequate in my opinion. I also found the headlight is bright enough to be seen in daylight, sort of like daytime running light brightness.
For comparison's sake, my wife's Breezer has an NX-30 dynamo hub with a Lumotec Oval senso plus halogen headlight. The light output of the IQ Fly is much better than the Oval, and the drag on the 3D71 is perceptibly less than the NX-30.
Just hope this helps anyone shopping for these. I'm not affiliated with Busch & Muller or anyone who sells them, just very satisfied with my purchase after a good few months of doing research and making decisions on the subject.