Great guide for Moto X battery replacement!
Battery was worn out from 2 1/2 years of continuous use, and had to be charged twice per day or more.
Repair was quite straightforward. This one requires lots of patience because of all the adhesive that must be dealt with. (This was the most intimidating part of the repair, actually.) I made an effort to take those steps as slowly as possible. Used several heating cycles before making first attempt at removing back cover, and made sure that the cover was quite warm to touch.
Trickiest part, I think, was getting the battery off the motherboard. It was stuck on really tenaciously. Again, patience, and a little gentle persuasion with spudger did the trick. FWIW, there's nothing but blank silicon under the battery, so no need to be scared of slipping the spudger under the battery a little. The adhesive is mostly on the bottom half of the battery, so a little gentle prying on the bottom left corner did the trick.
Replacement battery doesn't have any adhesive. Just for the !&&* of it, I used two little pieces of double stick tape (from a window shrink wrap kit) to keep the battery from budging.
Rear cover goes back on quite securely even without adhesive.
Take this repair slowly! Pause to take photos, read the news, live blog about your ongoing repair, whatever it takes to keep you patient, calm, and Zen-like.