I was sent a Platinum card in the early 90's since my monthly spending and prompt payment due to heavy travel and an expense account qualified me. Back then, it seemed like the perks of Platinum were good. If I'm not mistaken, it was by invitation only. I seem to recall using the card to get in to quite a few Airline Clubs without joining, by just showing my ticket and the card. I used their Concierge a lot from buying box seats at baseball games to hiring a Chauffeur. Traveling internationally it also came in handy.
I started my own business in 2001 and the card seemed OK for a while. The yearly fee was a tad steep in my opinion, and after a while, I seemed to loose perks. I was lulled away by my Bank's Platinum Business Card (non Amex). No yearly fee and the perks seemed about the same. I've been happy.
My S.O. Still has her Platinum Amex and has also felt that the advantages lately have been lacking. Perhaps it's just the economy, the sign of the times, or the fact that WAY more people have a Platinum card now. I don't know. I know that I'm very happy with my Bank's Platinum Business Card, and that She is fairly happy with her Amex Platinum. To each, their own.