That's the message Gmail shows me when there are no e-mails in my Inbox (because I just spent some time going through all of them to reach Inbox Zero).
 
It's funny that the message seems to imply that having no new mails is a bad thing (and that I should head over to Google Reader to read some news while I wait for new e-mails to arrive), when, actually, having no mails in my inbox is exactly what I was going for.