This looks interesting, and I'd like to play with it for sure. I bought into Hey early to get my email address, but didn't convert, and kept most of my email on Google.

This would be enough to bring me back to Hey I think, but only if they get interoperability right. I've tried calendars other than Google Calendar before, but when I have to interoperate with Google users (invites come my way) it's always hell. Me accepting their invite ends up with an email to their address with a .ics file, rather than actually updating a status in Google Calendar.

I think something like Fantastical (which pulls in all my calendars from different places) will probably remain my daily driver until someone does this better. Now I just wish they had an Android app.