I haven't had it long enough to comment on battery life.. maybe Homedad, you can fill us in on how yours is doing.
From what I understand these rechargeable batteries last a long time. I never had a problem with my 880 recharging and after a few years it's still charging fine, it was more a problem getting that remote to sit in the cradle right. The Harmony One fits snug and immediately charges once it's back in the cradle.
I'm not having any delay problems with my PVR, but as mentioned the response times can be adjusted.
