What's with the inverted screen when turning page?
Yes it's common with e-ink readers, but the duokan firmware shows it's not strictly necessary. Duokan will change page almost instantaneously without a full screen refresh. You can even set number of page changes without a full refresh. I set it to 100 and see no ill effect. Similarly, the Sony 650 will quickly flip through pages if you hold down your finger.
So it seems with a bit of clever programming, you can get rid of or at least minimize the stupid page turning screen flash. At least make it an option for people who hate the flash and don't mind having to deal with the occasional screen artifacts and manual refresh.