Entry in Shanghai. Exit from Beijing. Under 72 hours visa-free transit visa?

Hi there
We intend to travel around Shanghai & Beijing using this 72 hours free transit scheme from Sydney, on our way to Europe / USA. Is it worthwhile to do this? would it be too rushing around? We just want to see both cities, Great Wall etc. We will do all booking of hotels, tours, transport etc so that our time is not wasted in those 3 days. Your guide would help us a lot to plan our trip.
Thanks & Regards.....Bharat.