This thread is entertaining. I ordered and received the same extended battery and sloped back case as
gullzway's post in post 15. The battery so far has been great. It came charged at around 50%. I charged it overnight for 7 hours and when I awoke, the battery was fully charged and charging was in trickle mode (and there were no explosions LOL). The sloped back fits perfectly and snaps in without issues. The sloped back is kinda nice in that you can rest your index finger there when you are on the phone and makes it comfortable to hold. I definitely would not have liked the square backed case as the original poster had linked. The only cosmetic issue some will have is that the back is not black buy gray but for me it is a nonissue.
I believe that many of the Ebay mah ratings are over-inflated so I agree with CMeys that those battery ratings are inaccurate. I would withhold any conclusions, though, after one 8 hr comparison.
There are many posts regarding "cheap" batteries made in China. I am not a battery expert but this battery I bought is made in China, the OEM battery is made in China and the Mugen Power battery looks like it may be made in China (
www.unifirm.com) or at least distributed from HK. I have 2 other "1100mah" batteries made in China which, like the OEM battery, gets sucked dry equally fast with GPS usage LOL. The new extended battery does last longer but I will reserve final judgment until I have more time using it.
Personally, you can spend whatever you want if it makes you feel good. It makes me feel good to spend $16 for an extended battery and a nice back.