Thanks for posting this b01t.
I'm co-founder of Hiri. Saw a little traffic dripping in from HN so thought I'd chime in. A few things you should know about Hiri:
1) Hiri is a replacement for MS Outlook. It's Exchange/Office 365 and Outlook.com only for now.
2) What's unique? It helps you get better at email. For example, you shouldn't check your email too often. So we don't do notifications. Instead we encourage you to wait 30 mins before checking mail. Loads of features like that.
3) You can drag emails into a fully featured task list.
4) We've got a fully functional calendar built in.
5) Linux, Mac and Windows.
Would love to hear what you guys think.