I purchased a replacement back off ebay for $25, but I have read of people buying the sticker version cheaper and applying it inside the stock back themselves.
I have the Verizon variant with a slim tpu style case and charge it every night. Mine gets warm to the touch but not hot.
I started using qi with my LG g2 and cannot imagine going back. It's handy to be able to drop my phone in the charger in that dark, not having to worry about fumbling with a plug. It also saves on wear and tear on the micro USB jack.
Good luck! Hope this helps.
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