Ask any new buyer of expensive bikes and they will proudly tell you of the lavish upgrades they plan to do. New wheel set, lighter seat, pedals, drive train etc but rarely, would you hear the inclusion of the humble bell. After all, its so uncool to have one and it doesn't add to the whole image of faster and lighter.
But perhaps even more important than wearing a helmet, the function of the bell can mean the difference of running into pedestrains and causing serious injuries to both parties or a smooth and safe ride.
Especially when riding on shared pathways like I do here in Perth, the usefulness of the bell is played out 10-20 times each morning ride. It is a law here to ring the bell before overtaking so someone walking is shown the audible courtesy that a bicycle is coming through. Often, they appreciate it and step aside for us. Its quite fun too to hear our bells ringing together.
There are times when we fail to ring and this resulted in people getting an unpleasant shock and a few colourful expletives hurled at us. So if you haven't yet gotten one, don't wait. It is certainly a very necessary accessory.