I may be out of the loop, but my experience with it has been great. It's a (mostly?) open-source, self-hosted DropBox(ish) clone - with a great UI, web browser support as well as native MacOS, Windows, Android and iOS apps. (I figure there's probably some sort of Linux client as well? I'd have no idea.)
I'm shocked that Adult Swim isn't using something like this internally to work around this very issue. I'm sure they send copyrighted clips of shit to each other all the time for reference material. They've never run into this issue before? Even once?
Lesson learned - depend as little as possible on services you can extremely easy replicate on your own. When my free DropBox storage ran out years ago, I installed OwnCloud and have never even thought about cloud storage since. It 'just works'.