I love my bell. It is wonderful. It can save me from a 108 dollar fine from the bell cops. Not kidding. Other than that, it is the most useless piece of junk I have ever put on a bike. The rare time I am on a MUP with a bike, I find that a "hey how are ya, mind if I pass on the left?" is far more effective than "tinkle tinkle" pass..... Plus, I actually get to meet people ;p
Granted, when I am on a MUP, I am not generally in a hurry to get anyplace. If I am, I take the road which is usually (where I live at least) much much faster.
Cheers and happy biking