Thanks for this feature, I love to have my folder in bold, but there is a little bug on Windows ( 32/64 ), the first time, I downloaded the dev version ( previously I was using stable version ), I changed the value of bold_folder_labels to true but no effect ( even with the reboot of Sublime ).
I tried on my windows VM, same, no effect.
I finally success to have folder in bold by commenting then uncommenting the theme in user preferences. But each time I launch sublime, I have to do this operation to get back the folders in bold.
Here is the logs of the sublime console of my windows VM http://pastebin.com/4gGLz4vh