I just got this case. I did not want to get the Mophie. The fit is excellent and on/of button is perfectly flush with the case. The light changes when you press the button to tell you how much juice you have left. It is a 2300 mah battery for only $70 from Amazon. A much better value than Mophie.
From a fully charged phone and case I have so far got 14 hours of usage and 1 day and a half of stand by. I still have 50% juice left on the phone. I am very impressed so far.