Not really. I stay with Dropbox because, as others have said, it just works, and it does so across pretty much every major platform, both desktop and mobile. Cloud storage is their core product, and it shows. And the pricing really isn't that different from other similar solutions from what I've seen.

The few times I tried to use Drive, it was considerably more hassle to work with (and slow), iCloud was right out because it's Apple-platforms only, and my experiences with OneNote's sync issues makes me wary of trying OneDrive. Haven't looked at Box since I was under the impression it was aimed at businesses/enterprise more than individuals.

I disagree. As a long time paying Dropbox customer, I reevaluate each year, including copying all my data over to a competing provider to see how it shakes out. For all the big providers it's drag and drop. So far what keeps me coming back to Dropbox is that the other solutions have sync reliability issues on one or more of the platforms I use (we're a diverse family, with everything from a Linux server to OSX to Windows 10 to Android and iOS mobile devices sharing the same Dropbox account).