OK, ok, hang on. Only when I have to use it.
I work at a software company and we are a MS shop. I run Linux at home, and have since around '99. If I need to log into my work machine, I can launch my container that connects to the work vpn and does an RDP into my machine in about 10 seconds. Linux just works for me, even with MS (most of the time).
But I refuse to sync my phone with Outlook, for two reasons.
1. I don't want to check work email all the time, and have that expectation that I am always available. My time is my time.
2. I don't like like corporate policy, and I don't want their hooks into my phone.
That's how I use Office365 - if I need to check an email, my calendar, or look at a document on onedrive and I am not on the vpn. But that's it. It's a backup way of doing my job. It's slow but somewhat usable, but it is nowhere near ready to use all-day every-day especially in the corporate world. The fact that Excel/Outlook/Onedrive has to sync in the background has caused issues as well when "something goes wrong". And it does, often. Onedrive works most of the time, but when it doesn't sync it's a real PITA.