I know it's an oldish post, but I thought it would be useful to point out that the user.ini file that gets used on my installation is not that one. That is never used.It was under my user name folder / then applications / then witcher folder, then data/bin/config...
The path is 'Users/name/Library/Application Support/com.vpltd.TheWitcher2/GameDocuments/Witcher 2/config/User.ini'