A week ago I purchased the Light & Motion Arc Li-Ion unit from Supergo for $400. I bought it for my 6:30am rides when it's still dark out. I've only used it for two rides so far but it does a great job of lighting up the road, and the battery it also very small and fairly light. I've also noticed that oncoming traffic has no problem seeing me.

I have an old Specialized wireless computer and it does stop picking up the signal when the light is on.