The following procedure assumes that you have HTCdev unlocked your bootloader and can boot up Ramon RA recovery (or Clockworkmod recovery).
Step 1: Do NOT install Superuser nor its su file. With GB, one would use Ramon RA Recovery's menu item to install Superuser and su. However, even the latest beta version of Superuser and its su will NOT work on HTC ICS phones. So, step 1 is to UNinstall Superuser if you have installed it.
Step 2: Download the zip file for SuperSU, and place it on the top level directory on your SD card. SuperSU is a competing application and su which does the same job as Superuser. SuperSU and SuperUser is totally incompatible with each other and thus one must not have both installed. I downloaded the SuperSU zip file from XDA Developers forum. My copy is here:
http://db.tt/p7CerMda
Step 3: Boot up Ramon RA Recovery (or Clockworkmod recovery), and flash the SuperSU zip file.
Rooting is now done.
Success
Shake someone's hand
Profit
Regards,
Howard