HTC 8X has a very very slick design. Rounded corners make the phone feel extremely slim in your hand. All hardware buttons are easy to reach and press. All, but one, most important one - the power button, which is used to unlock or turn the smartphone on or off.
Guys from HTC's design department did exceptional piece of work an all, but somehow managed to miss this one detail. I think that my palms and fingers are what some may call average of size, but I noticed that I often have troubles reaching for power button (located on upper right corner). Pressing and detecting that firm response "click" is another hard thing to do when I do reach it after all. These shortcomings do not allow you to surely operate your device with one hand. I always end up increasing ringer volume if I somehow manage to put my index finger above power button and press it.
Though I rarely use my smart cell phone with one hand, not having this possibility makes me somewhat disappointed with my HTC 8X. Previously I used Acer Liquid S100, which has 3.5" sized screen and unlock button located almost at the top of a left phone edge. This, to my mind, was a better approach.