My only issue with any of the helmet mounted lights is their weight. I have been using the Bontrager Ion Pro all summer with regular night rides in Squamish & just discovered that the ratchet on my TLD V2 will not tighten past my regular setting. It is just about time to go back to my winter lid, but I hate to have to get another helmet after only one year.
Helmet mounted with integral batteries are the bomb though. I will not be using a separate battery ever again on a helmet mounted light.