OK, I've used the symbolic link method to make a Dropbox location for my saved games to sync between my two computers. Here is the MacOSX method for the Unix challenged (like myself):
On Computer A create a folder on your Dropbox folder. I called mine DoNotStarve. I didn't call it Don't Starve because I'm not sure if terminal commands can handle the space or ' in the name without resorting to special characters like %, etc. (Klei did the same with theirs.)
Next, on your hard disk go to Documents> Klei >DoNotStarve (These are folders nested inside your Documents folder)
Here you will see a folder called save. Drag this folder to your Dropbox\DoNotStarve folder. If this hasn't removed the original save folder from Computer A, drag it to the trash now.
Next open the Terminal app (located in Applications\utilities).
Type in the following:
cd ~\documents\klei\donotstarve
ln -s ~\dropbox\donotstarve\save
Next, on Computer B, install Don't Starve, enter the key, and update it.
Go to Computer B's Documents\Klei\DoNotStarve and drag the save folder to the trash.
Follow all the same Terminal instructions you did on Computer A.
This worked perfectly for me. I assume you cannot keep both apps open at the same time, though.
NOTE: You will have to install any mods separately to each machine using this method. I'm sure you could do the same thing to the mods within the contents of the app, but I have not tried it.