I don't like to rain on your parade but until the margins issue in BF is resolved, ebook readers on iPhone will not find it to be a decent replacement for Stanza. As it is, even with the smallest margins, the text still appears as a ribbon down the middle of the screen.
Now that io6 is here, we Stanza devotees are going to be searching for a replacement again. Bluefire started out strongly - pretty please sort this issue out! I for one would un-jailbreak my phone for Bluefire if it was necessary to do so.