It looks like EPUB — the open, zip/xhtml/css/xml-based document publishing format — is gathering steam. iPhone application Stanza has support for reading EPUB documents, as well as the already de rigeur 'sharing documents to iPhone from a desktop app using Bonjour and WebDAV on a local wireless network' that DataCase makes use of (or something similar) in the absence of a Google-hosted file sync/store for multiple document formats.
The desktop Stanza app can import PDFs too, converting them to text and so allowing the same reflow/pagination benefits that EPUB provides (but with the added risk of broken-ness that always comes with text extraction from PDF).
See also: iPhone + DataCase = Portable Digital Comic Book Reader