If its helpful, this is from the UK Centurion website (which isn't always super accurate)
St. Regis
Exclusive Centurion benefits include
•Room upgrade at time of booking, when available
•Complimentary daily breakfast for two
•6PM late check-out if available (4PM guaranteed)
•Your Fine Hotels & Resorts amenity, unique to each hotel
•Plus when staying two2 nights or more enjoy a USD200 spa, food & beverage credit
Soquite nice, not just once a year
MO beneifit I think remains as it is (I booked one today) but hasn't been negotiated and signed off for 2011 yet (which is similar to earlier years)
its a nice benefit