I must admit that I pretty much go to this bar every time I go to Sydney. It is unequivocally one of my favourite places of all time (and I've been to some pretty amazing places). I was introduced to this amazing, gobsmackingly gorgeous place by a bunch of Sydneysiders when I was out partying one night. Since that late night introduction, I've never looked back.
Okay, so here's the low down on the high life. No, you can't book seats at this bar. It's a first in first served basis, so ideally go in the off-peak times. There are periods where the staff are able to reserve your seating but that's only when it's quiet and even then it's not a given.
The staff are exceptional. Friendly, knowledgeable, and proud of their amazing city. How could you not be with the amazing Harbour!
I could go on but it's worth discovering for yourself. All I'll say is if you're in Sydney, just go! It's worth the steps and the non-direct pathfinder way from Circular Quay to the Shangri-La Hotel, to make a visit to the 36th floor.