I am the happy owner of an AT&T branded HTC One XL (On Straight Talk BTW). But if I was stuck with a locked bootloader/no root I probably would have sold/exchanged the phone quite some time ago for a phone with a unlocked bootloader (Galaxy S III etc), I happened to have bought my One XL from the XDA-Marketplace, and the seller already had it rooted and bootloader unlocked, but at the time when I bought it, it wouldn’t have been too hard for me to do that myself, thanks to a combination of a Root exploit, CID alteration (SuperCID) , which in turn allowed you to unlock via the official HTCdev unlock tool (Normally not allowed on One XL’s with AT&T “CID”)
But when the 2.20 FW version came to AT&T, it brought along a “updated” Hboot (can no longer flash kernels from recovery, must use fastboot :/ ) sense 4.1, android 4.0.4 and sadly full S-ON(was only partial before) and all root exploits were unusable, so the CID could not be altered and the bootloader couldn’t be unlocked (thanks AT&T :/ )
So the “2.20 Root think tank” thread on XDA was born, it took quite some time.. but finally a Temp root/SuperCID exploit/method has risen from XDA member “djrbliss” AKA Dan Rosenberg who is well known for rooting a good number of motorola devices.
Since 2.20 has full S-ON, “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.” – djrbliss
Dan’s new exploit basically temporarily roots the phone, then uses the newly acquired root privilege to overwrite the CID, in turn allowing the phone to be unlocked with HTC’s tool. After the phone is unlocked, a custom recovery can be flashed, and then either a custom rom can be flashed, or a SU+Superuser.apk zip can then be flashed if you want root with stock rom (why.. ?)
Check out Dan’s thread here http://forum.xda-developers.com/showthread.php?t=1952038 major probs to him!
After you unlock your phone, try giving my rom a shot :) http://forum.xda-developers.com/showthread.php?t=1907324 or maybe CM10, AOKP, MIUI or some sense based rom (if thats your thing :P )