I hadn't even tried it so I don't know what went wrong. I just know I saw more posts about them messing up root on MF9 with it than CF over at XDA. If you say it's that easy, I won't doubt ya.
Samsung Galaxy S® 4 MJA Rooted with CF Auto-Root Tutorial
HTC EVO Design 4G™ v4.0.3 Bootloader Unlocked & Rooted with HTC SuperTool v3
If it ain't broke, use a sledge hammer.