This is one of those topics that comes up periodically, and all kinds of opinions get expressed each time.

Mine is that I wouldn't want to ride my bike without a mirror any more than I'd want to drive a car without the rear-view. But I do most of my cycling on city streets where there's going to be traffic coming up behind me. If I was riding off road I might not care about mirrors so much.

If you have doubts about the sharpness of your hearing a mirror may well be worth a try. Again, people have their own opinions of the relative merits of various mirrors, but for me any mirror would be better than none.