i have a set of vistalite code 20's. The setup i have is a 15w on the handle bars, which has a remote switch near your thumb so you can turn on/off to save power when ever its not needed and a 5w on my helmet which is on all the time. It come with 2 batteries, 1 clips into a holder near your drink cage the other goes in your back pack. These normally give enough light for about 2.5 hour ride. I have used them heaps off road for single track the work really well. For fast fire roads there a little short in the distace you can see.
Before i got these i had my own home made setup with halogen lights and a 12v battery, but the no fuss of a good set of lights means they get used heaps more.
They cost about $250 about 6 months ago.