The iPhone 5 battery would not hold a charge, gave unreliable readings for percent of battery remaining, and ultimately just quit working.
The repair went quick and easy. It probably helped that I had replaced the battery in a iPhone 5S first, as I found that had a few extra steps that the iPhone 5 did not (home button related).
The repair guide was right on the money, the perfect guide. The screen cabling is probably the trickiest part of the whole thing, just making sure that the three ribbon cables are secured before reinstalling the cover for them. Actually, the digitizer ribbon cable was the hardest of the three, but still, not too much of an issue. The battery came out easy enough. The tab that should help bring the battery up, didn't. I did not have a heat source to warm the adhesive up, but I found I didn't really need it. I was able to slide the spudger down behind the batter and it came right out. The adhesive on the iPhone 5, is not nearly as tough as on the 5S. All-in-all, the battery replacement went very well, and relatively quickly ... new life for the iPhone 5!!
The replacement batter does not come with new adhesive strips like the iPhone 5S replacement battery did, so keep what you have in place the best you can. Part of the original adhesive came out with the battery, but I was able to reuse it. Ensure you press the new battery into place over the old adhesive to ensure good contact. Worked well for me.