Some more screenshots:
https://www.mobileread.com/forums/showthread.php?t=31303
I have a cybook and tried to use it for pdfs. It was frustrating. Now I have a DR1000S. I use it without preprocessing the files for all kind of pdfs and for the 99% is OK. I think the screen size is fundamental. But the DR1000S is still very young. Do not ask too much from it.