Cars around here are generally quiet (mostly EVs and modern ICEs with decent silencers) so I get a lot more warning off the radar. Maybe 400m. And it gives the opportunity to react - sometimes riding solo there’s a chance to dip into a layby and slow, to show a bit of compassion for the poor oppressed driver, which I’d have missed without the early warning. And I get more chances to wave cars through on blind bends I can see round. It definitely makes a difference, shows awareness and you’re not just mindlessly dawdling along. Had notably more thankyou hazard light flashes since I got it.
It also shows an indication of approach speed not just the fact there’s something there.