A very important feature of Kindle is to allow choosing font size. It make it an ideal tool for elders. But PDF documents have a fixed layout that won't allow resizing font conveniently, or you have to break it in pieces.
But, Amazon are probably more interested in selling their content, so I understand the lack of PDF support.
- It's cumbersome to do anything other than reading sequentially.
- The screen is still not big enough for letter/A4 pages - it does perform decent scaling, but you know how scrunched many technical papers are. Can go landscape and read half a page, which is a pain in two column layouts ...
- It's a tad heavy, almost like a hardcover textbook that needs to be held in both hands.
For graphical content, such as technical drawings/illustrations, wireframes or just B&W document proofs, the resolution and fidelity of an E-Ink Pearl screen combined with the true WYSIWYG nature of the PDF format across digital/print would be a dream come true for me...