HID are the way to go on trail. I'm using a halogen/NiMH dual beam system from Jet Lites (
www.jetlites.com). They're a dual beam system with 5 different power settings (6W, 9W, 12W, 20W and 32W) and have spot and flood beam patterns. They cost about $250 and I like the switching and water bottle mounted battery. I am very satisfied with the system - just right for me. I like using the various power settings - don't need much light when climbing, and full on lights on descents. In general, Jet seems like a good company- they've responded fairly quick to my questions (via e-mail)
I'm not sure how much your HID system costs, but if you can afford it, HIDs are the way to go. HIDs are more efficient in light output and energy consumption = bright burn and long burn time
I've been on the receiving end of on-coming HID lights and they do hurt the eyes, but are ideal for those behind the light.
My next purchase might be helmet mounted HIDs.