Updated 20-Sep-2023
Wow, what a strange week. People normally don't or don't have to change their email clients and calendar apps very often, but of course we can blame this one (at least part of it) on Microsoft. With the retirement of the greatest Calendar app ever (for mobile and desktop), Sunrise is... well... heading off into the sunset. What a difference $100m USD and 1 year makes.
For OSX there are a few options, none very satisfactory, but something will be found acceptable, most likely the native OSX calendar app (I try not to use anything based on iCloud). My actual email and calendar accounts are still Google Apps, but that can move without any problem, as access is using standard protocols.
But on Mobile this gets awkward. After an iOS update a year or so ago, which rendered Outlook nonfunctional (another app Microsoft bought and renamed), I switched over to CloudMagic on iOS and eventually on OSX (happy to pay the small price involved). But now with Sunrise gone, it seems to be time to switch back to Outlook, as now it has the integrated calendar (and who doesn't like that). Maybe I just haven't figured it out but is it impossible to put recurrence on a new calendar event, or even edit recurring events on Outlook on IOS? Nope, but no one said the new integration actually was finished (still, it is a damned sight far along).
So, Accompli becomes Outlook, which I then drop for Sunset and CloudMagic, then Microsoft drops Sunset and CloudMagic gets stale, and so now I'm back on Outlook. Well, at least for now.
Actually, on the Desktop, CloudMagic dropped the ball on their OSX client, introducing more bugs and awkwardness, and still unable to offer Thai language support (that every, single, other mail client can do). So, I've moved over to Nylas N1, which is a nifty fork of Atom. Yeah, it crashes now and again and uses a fair bit of memory, but (besides some awkward search functionality) really provides me a better visual overview and workflow.
Note on June 2019 - Nylas N1 in the form of Mailspring is still a great (the best?) option for desktop mail on Linux. However, their calendar functionality doesn't work (at least not yet). Everything else here is out of date (e.g., CloudMagic, Outlook on mobile, etc.).
I'm still getting off of Google products and services, but for now mobile is reliant on Google for both email and calendar. I'll need to set up both a mail server and calendar server to cut off of them, and then decide on which clients to use.