Good thing it was put to be optional. It would be even better if you will get a trophy for beating the game w/o using it. There is nothing wrong in implementing a button to help a player locate where the baddies are, but listen mode is just out of place. Its too exact. They should have made it more vague w/o being totally useless.
I was actually going to start a new thread about Listen mode but then I noticed people were moaning that there were too many threads about it so I, er, didn't.
Anyway, hear me out because I have an idea. I know a lot of people don't like Listen mode because they say it spoils the tension. I agree with this, however I still found it added to the gameplay in a tactical, stealthy way. So, why not include it in future TLOU games but only have it active in certain situations? For example, the game could take the Listen mode ability away from the player in a section that's meant to be especially scary or tense.
While the premise of that is acceptable, in terms of reasoning for when and where it is active and inactive, it would become annoying. Listen Mode could only be hindered if a section were particularly loud, like if you were escaping a burning building. Otherwise, to just have it disabled because the game says so, would be lame.