That was the only reason I almost didn't trade my S4 for an HTC One. Honestly, it was never an issue for me. On the m7, you held the power button for 10 seconds and it shut off.
Scared me at first when the M8 didn't do the same, but with a little experimenting, I found you just Power and Volume Up for a few seconds and it does the same thing.
Personally, I came from an S3 to an S4 to an HTC M7, and now my M8. I have never regretted going from Samsung and their Touchwiz UI to HTC's Sense. Hardware isn't much of an issue to me, since a massive majority of the apps will never reach the capabilities we have now. I would suggest making the switch
I'm tech savvy, but I'm far from a Dev. I am, however, always willing to learn, and welcome being corrected and taught new things!