It's very easy to use, it has all of my accounts in one place so that I don't have multiple apps open at once! The ability for me to send emails from anywhere via their mobile phone application would be great too!! Nothing really - everything works as expected but maybe more customization options? There aren't many third party integrations (yet) which makes things less flexible if you want something specific or different than what they offer out of box. Having access to your mailboxes everywhere helps keep track when using other applications like Evernote etc.