I have a hard copy of the first printing and an electronic edition of the second printing. I'd like to be able to switch back and forth as the situation dictates (I'm aware of the formatting changes that caused re-pagination) without fear of missing an important update if I were reading the hard copy.
Thanks for writing us about this. You can see changes that we made in the ebook and second printing on the book's errata page at http://oreilly.com/catalog/errata.csp?isbn=0636920010258. This page lists all confirmed errata and, if it's been corrected, the date corrected.
I hope that helps.