I use the Unified inbox to view my messages because I have 4 email accounts, and I have my preferences set to automatically mark messages as read. One of the email accounts, which is my school's Gmail-based account, is having an issue where none of the emails are marked as read when I open them in the Unified inbox-- I have to switch to the school inbox and re-open the emails there. Not a major issue, but kind of annoying when I'm browsing through lots of emails and have to switch inboxes!