Nice find! I figured out how to replicate this. When scrolling with the default web browser there's a delay before it resets. Just scroll with the browser and then quickly tap the top of the screen to open the notifications bar. It will keep it from resetting and enter it in a semi-permanent partial refresh state. Going to the Sony homescreen or opening an ebook with the Sony Reader app resets it back to normal.
This partial refresh trick is actually really helpful for whenever you need to scroll through lists like Dropbox and the file manager.
It also works with FBReader for perma-partial page refresh. It doesn't look too bad but the text is definitely rougher than usual. It makes page turns faster, especially when holding down.
Last edited by The-eBook-Reader; 01-14-2012 at 03:33 PM.