If you've ever unlocked a bootloader on a device before, you'll know that it wipes the data partition. Not normally a problem as long as you're aware of it. On the HTC One however, there are a number of applications (Calculator, Flashlight, Ringtone Trimmer and Sound Recorder) that are actually not in the main system partition, but are instead installed after a factory reset from a preload directory that lives in... the data partition!
Unfortunately, HTC haven't taken this preload directory into account in the bootloader unlock process - it gets wiped out and in turn those four system applications are gone... permanently!
Another potentially even more serious side effect is that because the OTA files check the integrity of existing applications, future OTAs won't apply if you've completed the unlock. The only way back from this situation is going to be a RUU (when one becomes available) - which will wipe your device again.
I've raised this issue with HTC and they're looking at it with the highest priority, but until such time as we have a resolution (or indeed just a backup of those 4 APKs?) then it's probably wise to hold off on the unlock.
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