As a relative newbie to Android I had lots of trouble deciding on whether or not to get the extended battery and more importantly to use an app killer or not. There's a lot of info out there and I found opinions going both ways. Here's what I did and the proof that for me, I was right. First, I got the OEM extended battery. At first the battery gave me 10 - 12 hours compared to 5 - 6 hours on the original battery. Good, but not great. With each charge it got a little better. Then, after reading a good article on NOT using app killers and seeing that 75 - 80% of my battery life went to the display("Settings", "About phone", "Battery use") I uninstalled my app killer. This was a week ago. Well my extended battery just needed a recharge at 15% and I looked in the settings under "About phone" and "Battery". I switched from the original to extended battery last charge(I charge my unused battery in the HTC dock while out of the phone). "Up time" was 32 hours and "Awake time" was 14. You can decide for yourself but I am convinced I made the right decision. I hope this helps anyone else trying to decide.