I like both the eReader Software and the Stanza software. I would say that Stanza's big advantage is that as long as you router is configured properly, sharing books between your computer and your iPod Touch is incredibly easy. eReader does have some solutions, but Stanza's works better.
Now, the beauty is that even though the development platform is not as open as it should be, the iPod Touch offers a far more open environment than the Kindle or the Sony readers. So ultimately, some readers can use eReader, others Stanza, Bookshelf or BookZ.