Not sure if it's been mentioned previously but there is one slight "gotcha" with the new platinum card.
I had previously already had an AMEX Rewards Maximizer Card with a supplementary card that my wife and I used for our personal expenditure.
I recently got my Platinum Credit Card also with a supplementary card that I was wanting to use for business expenditure. The idea being, gold for personal, platinum for business.
Looking at my account online today I noticed that my Rewards Maximizer Card had been cancelled and the balance transferred to the Platinum Card. When I called up for an explanation I was told that if you hold a Platinum Credit Card you are not allowed to have any other AMEX cards, something which I've yet to find documented on the AMEX web site. You can apparently have both a Gold Rewards Maximizer and a "regular" or "blue" card in your own name but if you have a Platinum card, AMEX will allow only the one card in your name.
The solution is to of course apply for an Additional Card which I can use for either business or private but you can't get a supplementary additional card.
When I was previously using the Westpac Amex cards which were both gray in colour my wife invariably used the wrong card for business expenditure and therefore the idea of having separate cards with different colours was quite appealing.
It looks as if I'm now going to have to use the basic Platinum card for private expenditure (for which my wife has a supplementary card) and for the few occasions where my wife has to make business charges she can do that also on her supplementary card and I'll start using the new additional card purely for business expenditure.
Ages ago my wife lost a credit card but I didn't bother reporting the loss to the credit card company, whoever found it was spending less than my wife was