I have found Dropbox a great tool to use with contract workers and other on any collaborative venture. It is a great way for sharing marketing tools with others we partner with and create a joined access to files.
The ease of incorporation into my PC for easy download to e-mails and files is a great way to seamlessly incorporate files into my communications and daily use. I can access files from multiple partners with ease.
There are so many ways to save my files and it is honestly overwhelming. Some use Dropbox, OneDrive, Google Drive and it seems as if there are 60 more choices. It make our technology sharing confusing and mired for where people keep files and how they choose to share them. While I realize this is no fault of Dropbox and simply the world of competition, your efforts to rise above and become THE resource could be a great boon to all. Clearly communicate what separates you from the pack.
Most universal to use with other partners and contracts. The other options still loom, but Dropbox is the most utilized and the one I prefer.
I have not switched. I use a few of the many out there to align with what others use.