I'm definitely in the camp that wished they were onscreen buttons and could be changed but I don't see a big deal about them being designed the way they are. Some manufacturers had their own button icons anyway and I know a preview of Sense and Lollipop showed the same buttons the M8 currently has as well. I remember the Razr HD had slightly different buttons than what my Galaxy Nexus has as well.
It isn't like suddenly with Lollipop they all do different things. If anything I think the older style buttons make more sense than a Triangle, Circle, and Square (and I love my Playstations).