Seriously. It's 2013. Make something that feels and has the space of a full-sized book. It's not that hard. Hell, use it as a loss-leader if you can't make the numbers work.
It's pretty clear that the consumers have spoken, and they value lightweight and compact and cheap over a large-screen. And Amazon would rather sell a stupidly cheap 5" model than a reasonably priced 8" one, because they just want more in people's hands.
Are you interested in a DX-sized device for reading PDFs?
And how good is the DX for reading PDFs anyway? They are smaller than a A4/legal page, which I image will mean that things will look small, unless you want to zoom in an out, which makes it un-book-y for me.
True, though I had a Pocketbook (902) and it was quite a finicky beast; customer service tried their best to help though. Also, it didn't have a "Pearl" display in those days though that might have changed now. I recall discussions on Mobileread where people had issues with Onyx as well. I wish BN would make a large-form e-ink reader: I have the (rooted) Nook and it is the best e-reader that I have ever owned.