See here:
http://www.hilton.com/en/hi/promotio...msType=program
Unlike the 2009 January sales, this years late check-out policy is rather weak though:
Late checkout and late breakfast policy for weekends
Late checkout till 6pm and late breakfast till 11am is applicable for Minibreak checkouts on a weekend (Saturday or Sunday). The local market defines the weekend and therefore in certain countries late checkout and late breakfast may only be available on a Friday and Saturday. Late checkout is subject to availability and will not be confirmed until check-in.