Taking a screenshot on Android continues to be a massive pain in the posterior. After three years and five versions Google still hasn’t incorporated this feature in the OS. And if that wasn’t bad enough there is no solution in the form of a third-party app on the Android Market, at least not without rooting your phone first. If you don’t want to root your only other option is using the Android SDK on your PC.
CyanogenMod has announced that they will be adding the ability to take native screenshots by long-pressing the power button in v7.1. It also brings back touch-to-focus on HTC phones. The v7.1.0 RC1 is currently available for you to try and has been deemed stable enough for daily use.
Unfortunately, this still doesn’t take care of the aforementioned situation as you would still need to root your phone to install CyanogenMod but at least you wouldn’t have to install a third-party app anymore, if that’s any consolation. But I do hope that Google wakes up and adds this function in the next version of Android.