If this device is also targeted toward readers of PDF (or other fixed-page formatted) business documents and ebooks, then a fine-grained zoom and a simple mechanism for transferring files would be ideal.
The Sony Reader's crippled two-stage zoom greatly reduces its usefulness for
reading some PDFs that are not specifically formatted for the device, since significant portions of the available display real estate are wasted on margins.
A much better solution is a variable-zoom display that allows for finer increments of zooming. Examples include the % magnification control provided in Adobe Reader or even better, the visually adjustable interactive zoom on the iPhone. I realize that the latter (as implemented on the iPhone) is unlikely because of the slow refresh rates on e-ink displays, but perhaps an e-ink friendly interface can be developed.
Including this functionality greatly extends the potential market for this device to all of those who use the ubiquitous PDF format for both ebooks and other types of business or technical documents. Like everyone here, I'm very much forward to seeing this new machine!