I have been using the "Multiple Inboxes" feature since it rolled in gmail labs out a month or so ago to keep track (using stars) of the emails I had read but still needed to deal with or address in some way. It was awkward though because the second inbox was displayed to the right of the regular inbox, squishing it and making subject lines hard to read on my smallish laptop screen.
Now you can display it above or below your normal inbox. It's a great way to keep important emails from getting buried. And once you're done with them, un-star them and they disappear on next reload.