I find Stanza pretty frustrating. It's ok for classics, but most of the new books I want to read are either not available as an ebook or available as an ebook only in USA.

I don't want a Kindle. I'm happy to read books on my iPhone as I prefer to carry fewer devices, only one in fact. However, there's a long way to go before books are as widely available (or as widely pirated) as music and video.