Once #9 arrives Monday that will be the last. Unless it's somehow perfect, I'm just gonna stick with unit #3, which I find to be the most tolerable of the replacements -- I managed to remove the aforementioned piece of plastic sticking out of the top inner border after a little fiddling. While it does have some blotchiness on the bottom, it does not distract me from reading as bright dust specs, scratches, and discoloration would. So, while not perfect, I can at least get down to reading.
I guess this is what can happen when you're an early adopter. The Kindle Paperwhite, Nook Glow, and Kobo Glow are all the first generation of front-lift ereaders, and neither is without its issues.