Blue is a good deal, and Blue Sky is a great (free) travel card. These do have limits, though... The article points out that the G/G cards do not have "pre-set spending limits," but AmEx will not necessarily approve any purchase made on the card. They have to be within a level that AmEx finds acceptable for that person's income and credit history, and consistent with past spending habits (i.e. you can't charge a Buick to an account that puts $1500 on the card each month).
At some point I might go Gold, so that I can eventually get the Platinum card, which is pretty sweet. The Centurion Card is black, but it's not properly known as the "Black Card." That thing is awesome. Personal concierge, personal shoppers, free companion tickets on international flights, free first class upgrades etc, etc, etc. I think you have to have had a platinum card for a few years, and be spending upwards of $100,000 on it. And then it's still by invitation only.
One day, I shall have that card
And yeah, VISA cashed in on the AMEX hype by making a "Black Diamond" card, or some such. It's got some game, but it's more for surgeons, rather than, say, moguls of various sorts.