My battery's health was about 50% after close to 1000 charge cycles. Phone was running very slow and battery life was less than half when the phone was new. Recently discovered Apple under clocked the CPU in a software update to keep it from crashing. Apparently the battery couldn't handle the peak power draw under load.
The repair went great with one hiccup when removing the sticky strips from the old battery.
Instructions were great and the tools provided where good quality.
I wish I read the comments associated with each step. Both sticky strips broke when I first tried to remove them. A few commenters said they heated up the back of the phone with a hair dryer and that softened up the strips for easier removal.
I was eventually able to get a hold of both strips with the tweezers that came in the tool kit and remove the strips.
The only other comment I have is I wish the instructions said which screwdriver head to use at each step. There are two different Phillips head screw drivers. One was not necessary for the iPhone 6. I think its only used in the newer models.