I did not really see the use case a month or so ago, when I trialed this out, mostly because of no Android app.. I came across it again a couple of days ago, and decided to try one more time.
Am I ever glad I did. With multiple email addresses, this thing saves a crazy amount of time. Add in using the Google calendar for appointments, and the onboard calendar for a quick monthly view and edit-and I am falling in love quick.
Add in Slack, Dropbox, and other in-app apps and it is a no brainer. The only negative is no app, but I am willing to wait.
Highly recommended, after a couple of days use you will wonder what you did without it.