FYI -- Just checked with Amex CSR on the HHonors card benefits.
Current 6x points categories:
Hilton hotels
Select U.S. drugstores
U.S. Gas stations
U.S. Supermarkets
Wireless, home telephone, cable, internet bills
6x points categories starting May 1st, 2013:
Hilton hotels
Select U.S. drugstores
U.S. Gas stations
U.S. Supermarkets
Wireless, home telephone, cable, internet bills
U.S. Restaurants