In reply to supersteve:
I've been pretty happy with an Exposure Sirius MK9 on the front, but only got it in the autumn, so can't speak to it's longevity.
Seems well built, lots of different settings via a single button which at first seemed confusing, but now I quite like. Charges with a non-standard cable (usb at the charger end, something circular at the light end).
Previously had something by Lezyne, which plugged directly into usb sockets to charge, but front battery was only really good enough for commuting.