My home built LED bike light performed well for many years, but when I got my new bike, the battery holder and handlebar mounting solutions no longer functioned adequately so it was time for a redesign.
I had been planning on a new simplified version, eliminating the micro-controller and putting in a simple dimmer potentiometer. It turned out I never really used the battery monitoring features and simply used a multimeter to decide when to recharge, and using a dimmer would allow setting the brightness easily and quickly and also allow the "high beam" mode to remain on through hazardous sections when necessary.
I was still pretty keen on building this myself as all it really required was cannibalising my old light for parts and making a new case. Commercial solutions had dropped a lot in price but are still many times more expensive than DIY (a few friends have these AYUP lights for example and they seem great).
Then I discovered semi-cheap LED torches as an option and ended up buying a Fenix LD20 LED torch and a small clamp from Ebay (that I can't find again, glad I bought 2...)
This puts out almost exactly the same amount of light as my old version but is in a small waterproof and easy to use package. As a bonus, it's a torch I can take camping etc. too.
I'm simply rotating through the NiMH AA batteries from the old light and am a bit disappointed with the battery life, seeming to have to change them more often than I'd like, but that's pretty quick and an extra set of batteries isn't too much of a struggle to carry around.
All in all, for $80 you can't go too wrong.