Thanks and awesome to hear! There's a much wider audience we're targeting - salespeople - but we got lots of excited traction with startup CEOs, and launched with a free tier of the product to see how it continues to garner traction in that usecase.
SquareOne (squareonemail.com) is a standalone native iOS email client that works with your Gmail account. We're in public beta with the app now.
The experiment we posted about (we're calling it MailOne for now) would simply supplement the new email UX by an added service layer, where the sender of an email is challenged to categorize it for you as the recipient.
Awesome feedback! We are actually at the moment working on incorporating intelligence into the app to make the sorting much more effortless. A lot more polish is also underway - thanks for pointing out a bunch of good stuff!
Happy you like the experience, and thanks for the feedback!
We're on a weekly update schedule, so definitely stay tuned and keep using and sending suggestions. Next week's build should have immediate push notifications for select zones.