Be aware that the Park Hyatt Sydney is scheduled to close for renovation for about 1 year starting in March 2011.

I'm the Hyatt forum moderator over on Flyertalk so do know more about details of Hyatt's program than I really care to know.

But for people getting the credit card - the perks vary according to the level you are at with the Hyatt program before you get the card.

Gold (Basic members) - get 2 free nights
Platinum (1st Tier Elite) - get 2 free nights + 2 suite upgrades on revenue stays
Diamond (Top Tier Elite) - get 2 free nights in suites

These are good for 1 year after your first use of the credit card - so time your application and card usage carefully (knowing that most here plan cruises way ahead of time).

While Platinum status doesn't really get you much in terms of upgrades and other perks, the one valuable perk that is given to Platinum (and Diamond members) is free internet.