For those looking for alternatives, I have been using Boxcryptor and it has been excellent. It includes a few more options (e.g. file name obfuscation).
. File versioning: Dropbox does a great job in versioning, so we wanted retain that flexibility.
. Collaboration for teams: This is one of the most important things that we wanted to address. So keeping file names as is the most simplest solution we could make use of.
Also, we are using keys. So strength of the password is a non issue and makes it much much harder to device a rainbow table attack.
Truecrypt would also work. Does dropbox do binary diff syncs?