I'm new to the Amex Business Platinum myself, but I can give you a little feedback about the multi-user situation so far.

We just got our first statement. We have the primary account owner card (platinum), one additional cardholder (platinum), and one additional cardholder (green.)

Though each card's usage can be viewed separately within the primary account, one single statement arrived when it was time to be paid.

The credits almost all need to be activated by the primary account holder, but then all those credits can also be used by the additional cardholder BUT they come from the same pool of funds. (So primary cardholder picked the airline for fee credits, but either card can do the spending that uses up our $200 credit pool, both of us being committed to the same airline for this.)

I can comment that it was much easier to activate the various enrollments for credits as the primary account holder. We happen to be a married couple, so I was present while both accounts were set up and I can access both accounts online. For the primary account holder, all the enrollments were easily done via the web portal in a self-service manner. To activate enrollment for the same benefit for the additional card, I had to use the website chat function (or could have called in by phone.) Linking Marriott Bonvoy accounts for the automatic Gold Elite status is one example I recall specifically. I have found it a little bit less than obvious which enrollments must be done by both platinum cardholders and which are active once the primary user has enrolled, but I *think* mostly only unique enrollments need to happen a second time for the additional cardholder, like the individual hotel elite status levels.

I can comment, for example, that the wireless credit was applied automatically when a cell phone bill went on the additional cardholder's account after the primary holder enrolled in that benefit.

I hope that helps.

--willo