Looks like HTC hasn't thought this through. They wanted to add just one button, so that they could add a fingerprint scanner and add the Home key to it. But Google has soft keys for Home, Back and Multi-Task.
So now there is a key that looks like home, but may not work like home, or may work like home and the soft key will confuse the shit out of the users. Feels like Samsung did a better job by sticking with all three hardware keys.