I was in the same position as all of you. New emails appearing and then vanishing, until I re-launched the Mail app. All day long. A nightmare for work productivity.
I like the layout and functionality of Apple's Mail app on the Mac, so yesterday I decided to call Godaddy about the 365 email. I just renewed my workspace email in January ($100), and the Godaddy rep offered to give me a full refund and apply the credit to 365. I kind of got the guy to admit that the workspace IMAP service is antiquated and therefore not as future-proof.
I had an intense folder hierarchy on the workspace IMAP server, so first I had to drag each folder onto the "On My Mac" section in the Mail App to save it locally and not lose my emails. Mail App is so good about this, that after 365 was up, I was able to drag any folders I want onto the Exchange server in the sidebar, and they were uploaded to the account as if they arrived there originally, and they seamlessly synced across all my devices. With Exchange, iOS defaults to sync "1 week", so if you're missing email, don't forget to change that to "No Limit".
Pros:
-365 is literally half the cost of Workspace email for 1 email account! (You can create free alias' for other accounts, like "info@", and they work immediately)
-It's working beautifully on Apple's Mail App on my Mac (the whole reason I did this), and still perfect on all iOS devices.
Cons:
-You need to edit a couple server based records (TXT, CNAME, etc.). The non-techsavvy will freak out, but Godaddy support is very good about walking you through it. I have my site hosted through aphotofolio and don't have access to server files. fortunately their tech support guys were amazing about doing it for me, and in less than an hour.
-Your emails will be offline as long as it takes you to wait for Godaddy's automated setup, and then while you edit those documents (roughly 2 hours for me). Do it at night!
I'm very happy. It saved me money, but cost me my evening. Workspace is 100% the problem, 365 is the solution. I'm still amazed that I'm receiving new emails on time and that they aren't disappearing! (It's aways funny to be so happy about something working normally)
PS. I would never have considered buying a Microsoft service, but I can't complain about Exchange. That's really all this is, but with a 365 wrapper.