I've heard of some overheating. I used to buy knock offs also but never had the same performance as OEM. I wouldn't buy this at $45, but you can't pass this up at $22.Looks like its out of stock again.
In the past I have bought much cheaper extra battery + charger on eBay. Are those not safe to use with Note 4?
I like using it because it saves the wear and tear of always plugging in your usb charger into the phone. You know those connectors get loose after the hundreds of times you plug and unplug it. I also love not having to worry about how much battery I have left.