Il Mio Problema
My father's iPhone 6 is a little over 2 years old now, and the battery is starting to go. Dying at 40 something % and not coming back on unless you plug it in. (The same issue Apple is covering for the 6s and blaming on "Ambient air" now???)
La Mia Riparazione
Repair went great. Screws were easy, getting the screen off was a piece of cake. Hardest part was the adhesive strips on the battery. Had to break out the hair dryer and practically bend the original battery in half.
Il Mio Consiglio
Be careful with the adhesive strips! Both old and new, they all broke for me. The new battery is in with only half of one adhesive strip but it sticks like mad so I'm not worried.