Hey all; When I saw the original email from Google, I think on Wed or Thurs, I immediately sent back a request. I received my invite on Fri and have been using it ever since. It's interesting, I'm still using Gmail as my main driver, but I've been trying to use Inbox a bit more. It bundles like emails under topics, so ad's and sales are bundled under Promos. You get the idea. I like the fact you can "snooze" an email and tell it to come back say when your at home, or at a particular time. I set a reminder for an email to show when I'm home and that worked pretty good. The only single issue so far is to trash an email, you have to do a dropdown, then trash. It should be on the main screen.
Anyway, hope you get your invite soon, the app had no way of sending additional invites or I would.