Comment 21 for bug 366963

Ubuntu Tweak exposes the "open with" setting for folders. Click on System -> File Type Manager in Ubuntu Tweak's sidebar, choose "All" for the category, find "folder" in the list of file types, and click Edit. This fixes problems similar to Revup's in a slightly more intuitive way, but it would still be nice for this setting to appear in Nautilus itself.

It is worth noting that even if you use Ubuntu Tweak to pick something other than Nautilus as the default application to open folders, (most?) file managers will continue to function as normal. For example, even after choosing VLC as the default application, I could still browse through directories structures in Nautilus, Dolphin and Thunar. The only changes were that VLC appeared as an "open with" option in the context menu for folders, and that gnome-panel Places used VLC to open folders. So at least in my case Sebastien Bacher's justification that "Changing the default doesn't make sense because when double clicking on a directory in nautilus you get whatever sofrware started rather than the directory open when you do that change" seems contradictory to what actually happens.