I tried iCloud briefly, but it was a no go for me because:
- App folders on the root directory mixed with personal folders is a mess. That reason alone is a dealbreaker for me.
- No cross platform client (web doesn’t cut it)
- Slower to sync than others
- No folder sync (at the time)
In the end I opted for OneDrive since I have an Office 365 subscription.
Apart from the weirdness of file names that @mat mentioned, it’s been solid for me.