After 2 1/2 years, the battery would not hold a charge well at all... Seems like a premature failure, but I thought it was worth saving $50 to fix it myself instead of having Apple replace the battery.
I spent an inordinate amount of time studying the repair guide and video to make sure I did everything correctly. There was tons of great advice on the user comments as well... especially the advice to rubber band the display to a can of beans so that it would be held steady so you did not have to remove the display and yet not risk damaging the cables. Everything NEARLY went perfect. Right at the end after I had stuck the new battery in with the adhesive strips, I realized it was going to be difficult to bend the connection cable the same way the original was to take up the slack in the cable. Thus the cable was protruding slightly. Instead of trying to fix it I forced it to bend down but this left a small layer of cable on top of the battery. When I reassembled the phone the display had a small pressure point from this cable and a small circular discoloration on the display from it. It was not a big enough deal to risk disassembling and reassembly. Frustrating that I nearly got it right but not quite after all the time I spent preparing. I will be able to do the next one perfect!
Pre-bend the battery cable the same way as the original before you attach new adhesive strips!