iFixit performs teardowns of flagship devices in hopes of helping people repair their own gear to reduce electronic waste. Don't bother repairing an HTC One when it breaks out of warranty -- it just has an incredibly low 1 out of 10 score from iFixit (compared to 7 out of 10 for the iPhone 5). iFixit says replacing components or even just opening the device is "extremely difficult". It notes, among other things, there are no visible screws, the display is "nearly impossible" to replace, and the battery is buried beneath the motherboard. It's not all bad, as the teardown acknowledged a "well thought out arrangement" in the internals and did note that the Android device's "solid external construction improves durability."

What Else You Need To Know

  • The HTC One features a 4-MP "ultrapixel" camera that gathers 300 percent more light, a Qualcomm quad-core Snapdragon 600 clocked at 1.7GHz, and a Sense 5.0 interface over the Android 4.1 operating system, and is set to be released in 80 countries.
  • HTC attributed delayed launch of the HTC One in select markets to supply issues, specifically problems manufacturing components for the Ultrapixel camera.

Other sources

If you can’t repair it yourself, take it to a repair store. They’ll charge you big money to repair a phone like this. - Dima Aryeh , DroidDog  
Of course, these days we don’t see many people repairing their smartphones, but instead buying new. - Robert Nelson, Android Community  
Phone Arena
HTC One vs iPhone 5 drop test results in broken glass, shattered dreams
Android Community
HTC One gets an iFixtIt teardown
HTC One Teardown: Even Harder to Fix Than the iPhone
iFixit breaks open an HTC One, literally
HTC One repairability scores very low, almost impossible to open without damaging
HTC One Disassembled By iFixit, The Name Says It All
iFixit Gives HTC One Lowest Score Ever for Repairability