I don't have any other directories in mind, but I wonder whether this should a ring (as it is in the example) or a typedef enum for forward compatibility (if the OSs add more directories).
Since it's unlikely people will upgrade to a new LabVIEW version and then decide to change the used directory in existing code, an enum is probably not required (the user can just delete the current ring and recreate it to get the new values), but I just wanted to raise the point.
Since the directories are relative to your app, why not do this yourself? OpenG, for example, has some VIs in its file package that can help with this, but it's fairly easy to write yourself.
Of course, you should note that if those config files are modifiable by the program, it's a problem having them under the executable's location because Vista doesn't like this. That's part of the point of the suggestions made by NI.