I don't like the default setting. By default this lab starts to display older emails that have already be read. You can change the default behavior by going to the General tab and picking a different behavior once you are out of new emails :
I like the auto advance newer setting so that Gmail displays the next new email. Once you are out of unread emails it drops back to the view of the folder/label. That's better than showing me old emails that I have already seen and likely don't want to take any action on at the moment.
Nice lab, but change the default preference setting!