How do you know when your battery is giving up?
Twice today, I've had my battery "crash" from about 20% to showing 1% after the phone automatically rebooted. In the first instance, I shut it off again, then when it powered up once I plugged it in, the battery monitor was showing 71% at that time (when it hadn't been that high beforehand), and then when it got to about 20% again, it repeated the restart and came up showing 1% again. I'm putting it on the charger overnight.
I figure that after over a year of daily charge/discharge cycles (at least one per day, maybe two...I'm kind of a heavy user), the battery deserves its final reward, but I still hate seeing weird behavior.