We trialled it for several months at work, and it failed in all sorts of ways. Not enough admin control, confusing to add employees, and -- worst of all -- sync failures where some employees sharing the same set of folders would just randomly not sync a bunch of the files.
This led to things like Alice telling Bob to look in the shared folder for a file, Bob telling Alice it wasn't there, Alice telling Bob yes it was, Bob telling Alice no really it isn't, Alice coming over to Bob's PC to see that hey it really isn't there, and then finally just emailing the file to Bob.
I myself got to deal with their business support a few times, regarding a bug that corrupts some PDF documents shared via Dropbox if they contain Japanese text. The "within 12 hours" response the website promised never happened -- it took days/weeks. They don't have any mechanism for me, as the customer, to follow or get updates pertaining to our support ticket for this issue (and it was kind of a show-stopper, since I work for a Japanese company). Finally, the fact that they have this type of a bug at all -- can't display international text? what decade is this? -- and that it goes un-fixed for 8+ months, didn't give us confidence in Dropbox.
If our experience is typical, I don't think Dropbox is going to do nearly as well in the business space as they've done in the consumer market.