I don't understand why people keep "blaming" Sony for the simple physical fact that there's no good way of viewing an A4/Letter sized page on a 6" screen

. It's not Sony's fault that PDF is a "page based" format and cannot sensibly be "re-flowed" like, say, RTF can, is it?
The only way that you could view A4 PDFs on the Reader would be to have some sort of viewing mode where you scrolled a "viewing window" over the page, and that really wouldn't be terribly nice to use, I suspect.
It's no use blaming Sony for this. They didn't invent the PDF format and aren't responsible for its limitations. PDF is a
horrible format for e-books; that's not what it was designed for, and not what it's good for.
Don't blame Sony for something that's not their fault, please.