I've been using the Cygolite Z-force NiMH for a couple years now and I am very impressed with it. I have used it for quite a few night rides and one 24 hour race and never had a problem with it. It is as bright as any other light I have seen plus it has a very long battery life.
I just picked up a Lume Strada wide beam HID. First ride was Wednesday night. Light pattern on the wide beam was excellent and no Niterider flickering bulb syndrome. The whole package was really reasonable (for HIDs). I'm impressed.