The Adobe Digital Editions upgrade to the Sony PRS-505 is brand new, but it it provides "industry standard" ePub support (no ePub ebook is ready until it works with DE) and as a "bonus" excellent PDF support. An Astak Mentor with eReader and Digital Editions would be a very serious competitor to MOBI-based ebook reading devices. The addition of DE would also allow Library ebooks to be read on the Mentor. It is possible to try out the PRS-505 version of DE using
Sony's Windows ebook Reader on ePub and PDF files. It provides a 600x800 reading pane in its standard view.
If PDF support is provided by DE, then the MOBI-only LiteBook won't have native PDF support, but neither does the Amazon Kindle. Like the Kindle, the LiteBook could provide DRM-free multi-format support by conversion to MOBI - but this would tie the LiteBook to a Windows Desktop for the conversion.