AT&T users may be happy to know that the HTC One X just got Root for the newer 2.20 Firmware! Here's a quote with the details below followed by a link with more details and instructions,
Source: XDAI have successfully rooted the AT&T HTC One X running build 2.20.
In the previous build (1.85), S-ON was only partially enforced, so it was possible to modify the /system partition without having unlocked the bootloader, in order to install su and Superuser.apk. This was changed in build 2.20: full S-ON is now in effect. As a result, it is no longer possible to write to /system even after remounting it as writable, since the S-ON feature has NAND-locked the storage.
In other words, it's impossible have a "permanent root" on 2.20 in the traditional sense without unlocking the bootloader.
I have prepared an exploit that gains temporary root access by leveraging two vulnerabilities and uses these newly gained root privileges to overwrite the CID ("superCID"), so that it's possible to unlock the bootloader via HTC's website. I'm sorry if you'd prefer to not unlock your bootloader this way, but there are no other options for root access available.