I leave home to go to work at 4 am so its uaually dark my whole ride in. I ride in the suburbs for the most part and street lights are scarce.
I use a whole nightrider lighting system (digital evoloution plus tailight) I add two more bright blinking LED tailights and reflective tape all over the bike and a reflective (Illuminite) vest.
I'm lit up like a Christmas tree!
I find the cars give me a lot of room when they pass me. In fact I think I'm safer than when riding during the day as I'm so easy to spot. My ride home is not so safe because there are more cars and there is a lot more for people to focus on when they are driving during the day.
One word of caution must be given to pot holes especially during a rainy or drizzly day. In the dark you can't judge their depth as your light will reflect off the top of the water. I learned this the hard way. I'm so leary of this now that I will mark the pot holes with white marker paint so I can spot them in the rain.