iFixit gives the HTC One a 1/10 in repairability (10 being easiest to repair).
http://www.ifixit.com/Teardown/HTC+One+Teardown/13494/1
The fact that the HTC One doesn't have any screws -- never noticed before -- is astounding. A real credit to the design.
I guess you would have to be real careful with the screen since they mentioned it's not easily replaceable.
HTC One Repairability Score: One out of 10 (10 is easiest to repair)
Very, very difficult (possibly impossible?) to open the device without damaging the rear case. This makes every component extremely difficult to replace.
The battery is buried beneath the motherboard and adhered to the midframe, hindering its replacement.
The display assembly cannot be replaced without removing the rear casethis will make the most common repair, a damaged screen, nearly impossible.
Copper shielding on many components is difficult to remove and replace.
Solid external construction improves durability.