I use the Mophie juice pack plus also. My 4s battery does last me easily all day long but it sure is nice to have that extra power for if you do happen do surf the web or download more stuff then usual. It also makes your iphone feel more solid, with out it i feel like im holding an egg and so carefull with it so i don't break the shell. All though the iPhone is a beautiful phone and since i work with automotive parts all day long and on concrete im using the case. I also had trouble finding a belt holster for it and i also bought a leather case made for the droid X. It fits perfectly. On the weekends when im not at work i sometimes put it in a smaller case. But if your lookin for a case/battery then the Mophie is the one you should get. I'm glad i bought it.