And suffers from the same underlying problem as Dropbox and iCloud: it's profit-driven proprietary software. Are you sure your interests as a user are aligned with that of Microsoft as a company? Are you confident that will not change over time?
Im not, and thats why I don’t rely on it too much. For backup I rely on backblaze - and i pay them for the service. Microsoft OneDrive is clearly a loss leader as it is so cheap when used in a family plan it is crazy!
Im more worried about my gmail reliance to be honest.
I'm confident they are at the moment. And i'm even more confident that if that ever changes, i'll find many people in a HN/Github thread whose interest are very much aligned with mine to fork the project and keep it going in a direction that suits us. Something you won't ever be able to do with a proprietary piece of software, unless of course you're willing to spend thousands of hours reverse-engineering a protocol they're going to change as soon as you achieve interop.