I'm quite pleased with a Cygolite bike light.

Because of turmoil at work, I wasn't able to bike commute last winter. So the 10-15 year old Cygolite I've been using as a helmet light has been sitting on the shelf for a year and a half -- charged up before it was put away, but it's still a Li-ion battery. Got it out so I can see through tunnels on the Greenbrier trail this weekend, turned it on, and the Cygolite lit up brightly. Nice! But just in case, I decided to run the battery down before recharging it. It ran brightly for an hour before I got bored, turned it off and plugged it in.

Worst part of the experience was finding a cord with a mini-USB connector to plug in; technology has gone through two more connector designs since I bought the light.