Having used Dropbox for personal stuff, and Box for work stuff, I have to say, neither has completely fit my needs.
Sure, Dropbox is great for working within small groups/teams, and for personal syncing. Sometimes the sharing functionality gets a bit wonky, but definitely the best implementation by far.
Box works decently well in the work environment, but it is definitely clunkier than Dropbox in a lot of respects. No one liked using Box where I worked (FB).
On my own, I've found that the most of my clients don't use any of these. In fact, they still try to run things on FTP sites! As a result, I've had to adapt to them and use Citrix ShareFile. It actually serves a different purpose than Dropbox or Box. It's a drop-in replacement for sending/receiving files to people within and outside your organization. I can silo off folders to specific users, companies, etc. I can send a link to folks asking them to upload files to me. It's definitely fit the bill in a lot of respects.
So internally, I still use Dropbox. But I don't expose that externally to my clients.
It seems that Amazon Zocalo is trying to compete with Google Drive, by allowing you to edit files in the browser, and integrate with your existing IT infrastructure. Not a bad tactic, but I think the service that will do really well in enterprise is one that merges the functionality of ShareFile into Dropbox, with IT integration.