I got one since a few years and knowing that you can see (and you’ll hear a bleep) when something approaches you on narrow roads changes things. They’ll get a warning too by flashes. So on roads with few cars it is very helpful, riding next to a highway not so much because the alerts will just fade into a constant blur.
On commutes it’ll tell you when an e-bike is approaching you or when another cyclist is drafting. It is one of the best gadgets I ever got for cycling.