Dropbox sometimes get's stuck for us (very annoying). We pay for google so have free google drive. We pay for office so have one drive.

We use dropbox as a poor persons collaboration tool. About 100,000 files in 20,000 folders. My major complaint - when it gets stuck syncing a quit on the app and restart of the app solves things - so I wish they would do that internally to the app, just timeout and restart whatever is jamming things up.

I do like the app / folders scoped permissions. For apps that play well there is an apps folder, and the app just has access to its own folder in there. A nice integration point for apps to dump files to for users to look at.