These things in particular made Inbox stand out:
* UI - simple, uncluttered mobile and desktop experience with uncomplicated keyboard shortcuts. It even had the little things like a satisfying sun animation when your inbox was empty! Desktop Gmail has a surfeit of widgets and add-on icons that perplex, distract, and confuse.
* Bundles - especially for trips: all the relevant emails I needed, in one place—unbelievably useful while traveling. All tickets and information aggregated automatically (and if not, easily added manually).
* Reminders / Compose access - fast interface for creating small notes and mailing frequently contacted people. No reminders equivalent in Gmail (Tasks are available on Desktop but not mobile) and the mobile compose on Gmail is a blank email.
* Pinning - sticky a reminder or email for easy access and reference later. I guess gmail's equivalent is marking as important or moving to inbox?
In any event, if any of the Inbox team are reading this: big THANK YOU for creating a revolutionary product that was a joy to use. I already submitted feedback through the app wishing it would continue but if there is anything further I can do please share how!