The best way to do this now is this:
Make sure iFuntastic is closed. Go to your HD>Applications>iFuntastic Support (folder) and open a text file called HomeScreenArrangement.txt.
You will now see a list like "com.apple...." . Type a new name after the "newName=" replacing the default name apps to your custom name.
Make sure there is a space after the"=" sign.
When finished, save your changes.
Now open iFuntastic. Go to Home Screen. You should now see the updated app names, yes? Now click "Update iPhone". Your iPhone will prompt you to "slide to unlock". There you have it!