The only real beef I had was them changing Sauniere from being Sophie's grandfather to being and adoptive grandfather. It rendered the entire Hieros Gamos ritual that destroyed their relationship moot.

If her REAL grandparents were engaging in the Hieros Gamos, there would be a very understandable attachment to the ritual: THEY ARE THE BLOODLINE.

If you really want to get clever, work in snippets from Hudson Hawk, Dogma, and Eyes Wide Shut. Maybe I should re-edit those films into The Da Vinci Code and see if I can get it to work. ;-)