My current employer is pushing us to Office 365. We have a lot of meetings that center around a shared document. The syncing in Word is extremely slow and in Excel we gave up on it entirely because we got constant merge conflicts with no clear way off fixing them. Outlook web is very slow and sometimes stopped fetching new emails till you reload. Meanwhile outlook for Mac silently doesn't show more than ten all-day events which lead to massive confusion during the holidays with our shared OoO calendar.

I understand that some might see offline storage and editing as advantages, but I've only seen it create chaos. It makes the file save dialog much more complex and I constantly have non-technical users mail files around like it's the 90s because they don't understand how to share it properly.