My iphone 4 battery was dying so quickly and after my Mophie battery pack died again decided to give this a try and change my own battery
the instructions were clear and precise, i made sure i had philip screws on my phone and bought the 00 philip screwdriver. I had to apply a little more pressure than i was comfortable with to turn the (3) screws and started to worry about possibly stripping the screw heads. The battery was glued tight so i had to use the plastic tools to pry loose. I did not have to charge my phone all day yesterday so I am a very satisfied customer
I wasn't too impressed with the quality of the "00" screwdriver (though it worked) i would pay a bit more money to purchase a higher quality 00 screw driver screwdriver.
The instructions don't tell you which area around the phone is the safest to leverage the plastic tool to pry the battery up , all it does is warn you not to damage the phone. This would be a very useful tip.