SYD is a close in airport, not that different from your own SEA. There is good transit, both low-cost shuttles but also subway. However, cab fares to Botany Bay are very affordable by big city standards. Certainly under US$25.

Is the Hilton still undergoing rennos through next year? This city centre property has been closed for at least a year now for major upgrading. It is quite central, though the Sheraton is also a good spot within walking distance of most major sites, galleries, museums etc. Good alternative, and likely where I'll stay since all my IC second weekend night certificates will have expired by May, and the renewal ones won't reach me until July...

However, will hold back on booking my transPacific flight until much closer to the event to wait and see what fares are on offer. [As an SE, can always get two reward seats in J unless the flight is completely sold out. A very, very sweet benefit, and no increase in the number of miles needed.]