You might be right about that — Rob's script had some instances where it referred to app id com.omnigroup.OmniFocus and that isn't correct if you have the OmniFocus from the App Store.
I made a version of the script that uses the other form of address. You can download it and try it out to see if it works any better:
http://dl.dropbox.com/u/971671/OPML2OF.zip
Let us know if that makes it work or not.