It was exceptionally useful as a student when I was frequently using lots of computers. As a sort of USB stick in the cloud (with added shared-folders) it was brilliant. The sync, versioning and useful web interface "just work".

I can completely see that if you're a small team and are faced with the problem of shared folders, dropbox would be a good solution. It's not too expensive and a lot easier than setting up reliable and secure self-hosted file storage.