I'll also agree with the PDF shortcomings for large-sized formatting but with the caveat that if you are making them yourselves you can size it to the reader and it will look fine. (Though of course most of us have the problem that they are already made and most definitely NOT for the small reader screen.)

But my main gripe is with book organization. Basically it tosses all of your data into one big pile and then makes you sift through it 10 items at a time (if looking at it on the reader). Not so bad if you have a few dozen books but with all the space in there it can be very easy to end up with many more (Currently have 153 on mine. But to be honest, quite a few are things like book and music inventory's, personal info, itinerary pages, restaurant menus...all sorts of general info that I find nice to have handy.)