This is timely thread! I've been researching and shopping for a good charger and some rechargeable NiHM batteries. Most of my applications require AA & AAA batteries so that's what I will be focusing on. My smoke detectors are hardwired with 9v battery backups but I don't feel rechargeables are worth the effort or expense since the battery in a smoke alarm lasts a good while and nothing else I own uses that battery.

I will say though that CR123A "primary" batteries are a very important item to me. My Surefire lights don't seem to be very compatible with the few rechargeable batteries I've found in that form factor. My Surefire E1B backup is by far the best light I've ever used, and I have a couple other Surefire lights that I also like. While I have lights that use AA & AAA I plan to always have at least two dozen batteries on hand at all times for my Surefires.