Terry Pratchett's Hogfather will be running on ION television on December 23, 2007, 7 PM, 6 Central.
I just saw it on DVD. It does a pretty good job selecting a cast that matched my image of the characters from the book, particularly Susan Sto Helit, Best Governess Ever.
Pratchett’s Ankh-Morpork is a Shire-like temporal stew, where waistcoats and tobacco meet mailshirts and magic swords. The film version skews more 19th century than the Discworld I imagine, but I can understand why.
A 19th century ambience makes it a lot easier to provide settings and props. And many of Pratchett’s audience have as part of their mental furniture a prototypical urban Christmas fantasy featuring anthropomorphic personifications, including a tall ominous one shrouded in black. Dickens A Christmas Carol was published in 1843.