Just my $.02 worth. I got my TB on Monday and had ordered the extended battery. Over the weekend I was really happy about the big battery. When I got it I put the big battery on. I don't mind the extra size, but I thought after I finish all the setting up and playing maybe I could use the small battery. Also with the big battery I left the brightness on auto and the only other "battery saver" thing I did was the Blockbuster deal. I use my phone for business and pleasure. I get a few emails and calls and texts a day. Some days are more than others. Today was about average. I don't know where to go to get the breakdown of usage either. I leave the phone charging all night and turn on at 5:45 AM. It is now 4PM Maui time and my extended battery is showing 56% left. I am sure on the little battery it would be dead by now. My thought is if this phone has heavy business, the only good option is the big battery. I don't want to change batteries during the day if I can help it. I am staying with the big battery and the little guy as a back up. For reference I am coming form a Storm 2 and I only had two regular batteries. There were days that I would need to use the back up battery. It really is an extended battery phone if you want to use everything IMHO.
Aloha.