Exchanges in some areas are full because nobody wants to invest into building new capacity since government has volunteered $50bn to make it all redundant. The problem has been created by government by announcing NBN in the first place.
I'm still not convinced. How is ability of users being able to send each other high-resolution images, HD video etc. going to be worth $50bn+ to economy?
The reason why upstream is so slow is because there is hardly any demand for it. Some ISPs will double your upstream on ADSL2 by reducing your downstream speeds. Hardly anyone is interested.