Yes, I use a mirror. Nearing 60 years old my neck doesn't turn like it used to and seeing behind me can be difficult. I was using a Third Eye mirror that mounted on the end of my handlbar, but after switching to a more swept back style bar that mirror just didn't work. Switched to a something with an arm that clamps to the handlebar (Magic Mirror, I think it's called). Just mounted it yesterday and haven't had a chance to test out, but it looks promising.
Tried helmet and eyeglass mounts and they didn't work well for me.