Inbox by Gmail has been updated by Google in order to work perfectly on the iPad. The update includes a few changes to the way the application works and it’s organized, especially considering the switch from iPhone to iPad.
The app is still an invite-only affair, but usually if you send an email to inbox(at)google(dot)com, you should be able to get an invitation pretty fast. The app is also out on Android, obviously. The new version available on iOS right now is 1.2 and in the meantime it seems the Android version of the app hasn’t been updated for a couple of months.
The usual bug fixes and performance improvements are included. Inbox by Gmail features Bundles, a function that bundles similar messages together so you can deal with them all at once. Highlights is another feature, that shows the most important info from the messages without opening them. Reminders is another useful function, as well as Snooze and Search.