Ever wanted to quickly switch between Gmail and Inbox? You can add Inbox to Google's app launcher: just go to inbox.google.com, click the grid icon at the top of the page and then click "add a shortcut". Drag and drop the icon to change its position.
I placed the Inbox shortcut next to Gmail's shortcut.
Inbox has a setting that lets you redirect Gmail to inbox.google.com, just in case you want to switch to Inbox.