Seems that Hilton wants to get a off to a good money saving start for customer wishing to book weekends for the whole of 2012 (well after about 16th Jan from what I can see). Rate do seem pretty good:
Rates for London:
A random check on the Hilton Brussels City shows a good discount on the ordinary Pre-Paid rate for the Deluxe Room of EUR61.
There is no list of North American hotels but you are encouraged to search. A choice in April, for 1 weekend night at the Hilton New York yielded a saving of $101 per night
If you know your travel plans in advance these rates do represent a very good deal across a wide range of cities for a large part of 2012.