I'm not sure about the UI of the menu... the folders make it look kind of old school. I know I'm being picky, because I'm liking the rest of the design, but I'm still trying to find a proper Mailbox replacement... sigh
You should spend some time on the UI. It doesn't feel as good as it could be. If you can make it happen that all the features are in with a smooth, minimalistic but elegant design, you can attract more users who spend more time on the app.
