If you use quality LED style headlamp eg Busch and Muller, then you should find it sufficient. You can always add an additional lamp if you feel underlight. I ride on normal city roads and some dark paths and find it plenty.
The optics are bike-specific so you get a concentrated rectangle rather than a generic circle of illumination.
With LED you should really use a rear lamp but they work OK without.
I use the higher grade Shimano dynohub (with disk brake) and its a great piece of kit.