ZuluReader will support epub files within a week or so. Basic RTF's (no tables or images and with a uniform font size) render really well now. So I am full speed ahead on supporting epubs. The speed at which I'm getting through this is a testament to the epub format... it really does rock! In fact once I'm finished I think I'll drop RTF support altgoether.
The DRM free ebook website I am developing (ZuluExpress) is also going to be converted to an epub only zone. That's how confident I am that the epub format is going to very quickly become THE format for eBooks.
You can download ZuluReader here www.zuluexpress.com