Thankfully neither my wife nor I have noticed any significant issues with 6.3, other than the occasional grey icon. She reads on it, I don't, but neither of us have noticed changed in battery life or any other untoward behavior.
Still it would be nice if a fix updated is out presently.
By the way, I found a workaround to having to restart the device to get manually downloaded files in he book and document folders to show on shelves: Force stop the Kindle App from Setting|Applications. When it's started a gain, new book files will appear as expected. I don't know how good a practices this is, but it is a bit faster than restarting.
ApK
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