UPDATE: Hey everyone! So the batteries came on Saturday. Unfortunately I was too busy to mess with them till late Sunday night. Please bear in mind while reading this that I've yet to give the batteries a thorough testing. At the time of writing this I've used one of new batteries for just over 2.5 hours. I will update again once I've had a chance to go through a major gaming session 4-6 hours or more.
Initially unpacking I was impressed the batteries each came with a USB charging cable for the controller & a small microfiber cloth to serve as a work area for the change out.
The first battery would not hold a charge at all. The light on the controller just flashes in quick succession & refuses to operate once unplugged.
The second batteries black wire isn't connected to the battery, just kind of free floating. I will be attempting to connect this & in my next update will tell whether or not the battery works.
Battery 3 worked flawlessly & it's the one currently in my controller. When I saw it worked I began the switch out of the original controller battery to my gold wireless headset. I plugged in both to charge & after about 20 minutes the lights went out, signifying they were ready for use. I proceeded to use the new battery controller & headset for 2.5 hours with no issues, or bar drop on the battery status screen for either unit. Under normal operation with factory batteries, 2.5 hours would be 1-2 bars left on both.
I have not opened battery 4. I will mention it in my update as well.
Also, I feel it note worthy to mention that with the first two batteries being problematic, I wrote the supplier to alert them to this. If I receive a response I'll include that also in the next update.
In close I would say that while the Amazon batteries are a gamble, I got 4 of them for the price of 1 from Adafruit. The previous order I placed with Adafruit prior to ordering these batteries off Amazon resulted in a battery which wouldn't charge. I returned the battery to adafruit & got a refund minus my shipping & handling (which they overcharge for). No matter which way you choose to go, this seems like a worthwhile upgrade for anyone feeling adventurous enough to delve into their electronics. I will update as soon as I can though with Christmas this week, I'll probably be after that but before the new year.