The typeface was easy to read (much easier than reading email or web pages on the iPhone,) the application automatically took me back to the last page I was at, and there was no need to keep the lamp on if I wanted to read at night (an occasional bone of contention in our house) and I didn't miss the feel of the actual book anywhere close to what I'd anticipated.
It's definitely a habit I'll keep up, especially if Stanza keeps getting more and better titles.
UPDATE: Even cooler: Someone from Stanza got in touch with me on Twitter to thank me for the post and to ask for any suggestions. Nicely played.