Today, Google finally stripped Inbox of its invitation requirement. If you've wanted to get in on the email-as-a-to-do-list action, you can now sign up for Inbox directly.
Not only are invites no longer required, Inbox has also added some sweet new features, including Trip bundles. Much like how the Purchases bundle puts all your shopping-related emails together, Trip bundles will collect all the emails you have related to travel in one place.
The app also now allows you to set Delete as the default function, instead of Archive, and you'll get even more suggestions for Reminders. If you want to get started with Inbox but haven't yet, just download the app here. If you're a Google Apps user, ask your admin to enable the option.
Thanks to you, Inbox by Gmail is now open to everyone [Official Gmail Blog]