If Delta keeps up the promos with Amex you could do better with the non-Delta Amex Platinum card. This past year they gave you 25k MQM + 75k RDM for 50k Amex MR points ($50k spend or $25k spent on travel as you get 2 MR points for $1 on travel). This is better than the Delta Platinum (only 20k MQM for $50k spend) or Delta Reserve (30k MQM for $60k spend).
The Plat Amex also gets you SkyClub access plus access to Admiral Club, US Airways Clubs (and can be flying on any airline for these clubs) plus hundreds of other airport lounges across the world (including Oasis at JFK T4, e.g.).
In addition you get $200 in travel fee expenses refunded annually (baggage fees, food-on-board, award redemption taxes/fees, even gift-cards...that's right, airline gift cards).
There is also no foreign transaction fee with the Plat Amex (2.7% on the Delta cards).
To each his own, but in my opinion there is no benefit to the Delta Platinum or Reserve card if you already have elite status. You can do better with other cards now that the gift card redemption is not worth it anymore.
I agree IF Delta keeps up the promo with the platnium card. Even though the annual fee is $450 a year, I would switch if I knew they would keep up with the MQM promos. I just hate to get the card and then have the promos for MQMs no longer be there.
If I was able to keep PM status without doing mileage runs with BIS miles on regular trips, I would definitely not bother with the card.