Reuters has a report on the Harry Potter sequel with ILM's help:

Christopher Columbus, director of "Harry Potter and the Philosopher's Stone" and now the second wizard saga, is fiercely proud of the advances made in special effects from one film to the next.

"To me as a filmmaker it was so exciting. I was like an eight-year-old kid again. I couldn't wait to get to the set," he said of the 11 months spent filming "Chamber of Secrets."

"I think the effects are much better in this film. I realized after doing the first film that you can basically do with technology today whatever you want," he said.

Columbus paid particular tribute to George Lucas' Industrial Light and Magic special effects company for creating the bedraggled and forlorn house elf Dobby for the new film.

This film is much darker and edgier than the first, with Potter being chased by fearsome snakes and spiders in some spectacular action sequences.

Columbus was worried that he might terrify children around the world. His fears proved unfounded.

Thanks to Fuufuuu for the link!