If you haven't had the chance to go for a moonlight ride, go do it right now. It's OK, I'll wait.
This week I have been riding home with my headlights off (once I get off the road). I actually prefer the low light conditions to having a headlight for a few reasons.
Riding with just a bar light gives a tunnel vision effect--everything ahead is clear, but everything to the sides remains a mystery. It's quite easy to see, but I don't like not being able to see to the sides.
A head mounted light I really don't like for commuting...it makes it easy to see wherever I'm looking, but it also makes it far too easy to inadvertently blind oncoming drivers. I don't want them blind. I also have a tendency to want to play with the light, in the sense of trying to look at everything off to the sides. "I wonder if I can see the creek through the trees...yep! Can I see the tops of these trees I'm riding under? Yep! Crap, am I running off the trail because I'm not paying attention? Yep!"
Riding in moonlight is something completely different though. Monday's ride had a not-quite full moon, but I had a well-defined shadow in front of me the whole way home. I could make out every important detail of the trail, though it was very grey. Tuesday was overcast and it was pretty similar--I didn't have a shadow, but I could still make out all the details I needed to. Wednesday was the best, it was raining lightly and the trail was like a mirror. turning the light on didn't illuminate the trail any better than running with the light off, it only made trailside features more visible. Night rides in the rain are an awesome way to gain a new perspective. Rain gear gets hot when the temperature is hovering just under 50, though (I had the pit zips on the jacket open, at least).