According to MobileRead:

Starting next quarter, Stanza, the well-known e-book reading software for the iPhone, is going to support DRM-protected ePub and PDF documents.

This is quite interesting, as one of the main arguments against PDF (in the comments on this post)  is that it doesn’t work on handheld devices, and doesn’t translate well to screens. But, PDFs already work quite well on dedicated readers like Sony’s and Foxit’s. If you add viability on iPhones, that’s a wide range of devices that will read PDFs, and it makes the hill to climb a lot steeper for ePub.

[via MobileRead]