The guys with rim brakes in our summer bicycling group don't need a bell to warn pedestrians. All they have to do is grab some brake. The squealing instantly makes pedestrians jump off the multi-purpose path. The sound just screams Wal Mart bike even though their bikes are not big box store bikes. No thanks. I will stick with my hydraulic disk brakes. I don't need a marketing guru to tell me that.
I don't know much about the new hydraulic rim brakes, maybe they are way better but I can't see stopping over 300 lbs going down hill with rim brakes.