I was taught to use "not at all" as a rather polite, standard reply to "thank you". However, I don't see it being used at all nowadays. Can I still use it? Would it be widely understood? Should I be aware of any differences between using it in British, American, Canadian, and Australian English? (As in, are there better alternatives in any particular dialect?)
Edit: A (German) friend of mine who spent a year studying in Edinburgh says "not at all" is still fairly common there.