I’ve mentioned Professor Bob Johnston before but it appears he’s also a favourite of the Institute of Customer Service. Based upon his research they’ve published some brief guidance upon how to best manage them. They’ve also published various reports commissioned by them from researchers such as Bob.
There are some words of wisdom such as:
“A complaint is a gift and you should consider yourself lucky that a customer is prepared to give up valuable time to help you improve your organisation.”
“One can learn so much about problems with internal processes, training, specific employees/managers, and product – free”
“Do you have a continuous culture? Do you check customer (and employee) satisfaction regularly?”
There’s also a comment here from Vicky Sargent who does much work on the web metrics side of Socitm – she’s seen councils where monitoring feedback makes a difference to their services!
Posted by greatemancipator 
The Great E-mancipator 