kiai are great. its especially amusing to hear each individuals kiai and i think it gives you some idea to what kind of person they are and what kind of training they do and where their centre is, it can probably tell you a whole lot more too.
i think my favorite kiai though is a yudansha woman at my dojo who growls..... i am woman hear me roar! hahahahhaahaha
oh and i train iwama ryu and kiai is just a normal part of training, i would love to know what the people walking past our dojo think, especially during a vigorous weapons session!
although i dont understand how you lose your voice or hurt your throat, for me kiai doesnt come from the throat, it originates in the abdomen and isnt a strain, rather a natural sound that escapes when the hip or centre locks into position, usually accompanied by a little tingling sensation just bellow the belly button. growing with intesity as power develops in the individual.
oh and Mr P, sounds like a good opinion to me, sometimes you feel like a kiai just isn't neccessary and the technique will in fact feel a lot softer.