Besides the fact that the card itself is made of a metal that is generally worth more than $500 per ounce, and has text engraved in it with real gold, there is no pre-set spending limit. Apparently you earn double points for travel, and one point per dollar for everything else. Perks include such things as rewards in the form of private jet travel, British Airways free companion tickets, and complimentary upgrades to 1st class.
The status symbol value of cards in this realm are one of the biggest selling features, for people who crave financial status. Other benefits cited in a nearly 60-page benefits guide from the card issuer a few years ago included access to worldwide airport lounges, hotel burglary insurance, and emergency travel evacuation coverage.