Thought i'd come back with some feedback on doing the Harbour Scenic, which I've now done three times and will be doing it a few more times in the coming months as friends and family ask for it.
With all the research from here, the VFR guide and ERSA I was prepared to do it solo, however the school I rented the Citabria from encouraged me to go with an instructor (they didn't mandate, but strongly encouraged) the first time. I had very little input from the instructor, but did glean a few tips which made it easier.
So with a flight plan filed from Camden DCT PSP PRT HSY LRF HBB MANLY SECF, lifejackets and ELT in hand, I flew the route at 1500ft, called into Sydney Centre at PRT requesting harbour scenic, then before reaching LRF was transferred over to terminal and then at LRF was given a Harbour Scenic 1 (with another frequency change), direct to the Bridge performed the orbits and then requested Victor 1 South. Followed the harbour out at 1500, then after clearing the heads was cleared down to 500ft, and then onto the Victor 1 frequency. Chose to stay at 500ft up until SECF, but could have climbed slightly earlier. On the third time I did this route I was only cleared for Harbour Scenic 2, and then at Chatswood CBD they had a change of mind and cleared me to the Bridge.
Traffic wise, the first pinch point was meeting the traffic in/out of Bankstown between Prospect Reservoir and Pennant Hills. Going onto Harbour Scenic 1 you are of course well above the seaplanes and helicopters in the Harbour, however when you come out and descend into Victor 1 things get a little busier as you join the helicopter traffic (and anyone else on the route), the radio seems to get quite busy at that point working out where everyone is.
I feel that if you read the procedures, can use the standard phraseology on the radio, can hold a heading and altitude accurately then it should be quite straightforward. The ATC seemed really good, friendly and helpful.
Thank you for all the comments, particularly mnewbury.