I just spend 5 nights in Sydney at the PH and then 3 nights at the Melbourne PH. Both hotels are really nice. I highly recommend getting the breakfast at the Sydney PH.
PH Melbourne has a lounge. I paid for the stay and got lounge access with points. The lounge is nice, great view, not too busy and food for breakfast and drinks at night was fairly good. definitely worth the 3000 points I paid.
Melbourne PH has bicycles so if you like to cycle make a reservation; they are free.
this is a link for free walking tours in Sydney and in Melbourne. I enjoyed them. make sure you tip
http://www.imfree.com.au/
I took this tour to the blue mountains (its actually a nice day out of the city) and for the city tour which was excellent
http://www.bluediamondtours.net/
In Sydney make sure to talk a walk through the botanical park. Bondi beach is overrated.
I had a very nice dinner at
https://www.ponydiningtherocks.com/
a little pricey but very good food and excellent service.
I also liked this german food place. nothing fancy but really good sausages
http://www.munichbrauhaus.com/food-2/
In Melbourne you must visit the Queen Victoria market. some great food stalls both to eat there or to take back to the hotel.
Also take a bus or Uber to St. Kilda beach. a little funky but great vibe.
I used Uber in most of my trips. If you do not use it now, download the app and register. cheap and convinient.