There were whispers around the internet that AT&T would keep their HTC One from being bootloader unlocked by the HTC Dev site. Luckily, it can be unlocked right now! Those who were lucky enough to get the HTC One early from AT&T have confirmed that it can be unlocked with official tools, just like the international version. The root and ClockWorkMod recovery procedures are also the same as the international model, so it should be very easy to mess around with.
However, there is one thing to keep in mind. All of this can change on launch day. If you remember, the Verizon DROID DNA could be unlocked with the official tool, but soon after, the tool stopped working. Either HTC or Verizon blocked the device from being unlocked, and the same could happen to the AT&T One. However, we hope for the best.
If you do decide to unlock it, keep in mind that it voids warranty. It’ll also wipe your phone, and remove a few “system” apps, like Calculator, Flashlight, Ringtone Trimmer, and Sound Recorder. You’re also forfeiting OTA updates, but that should be standard fare for many of you modders.