Well they have me because Google Sync doesn't seem to work half of the time and/or takes forever to sync on all of my devices, and OneDrive and iCloud don't have clients on Linux (really?)
I use Dropbox, but I might switch to Mega in the near future. The better storage capacity and leaner UI speaks to me. I haven't had any issues with the sync client so far either, though I've only tried it on Windows.
In a way yes. If you told people 20 or 10 years ago that in 2017 Apple would be #1 company in the world and have the browser with the second most users (with the first NOT being IE) people would laugh at you.
It’s so bad. My work just switched to Google from Dropbox and it performs much worse. Also everything about the client and the product just screams that Google doesn’t give a crap about it.
To be pedantic you mean the POSIX userland. Office (including its OneDrive integration) does ship on Linux, albeit under the Android userland which doesn't help you if you want to run Ubuntu.