Nope, I haven't seen the movie (it's not out yet), but I did finally get around to reading the book. And boy, I can understand why various Christian organisations are pretty pissed about it.
The book - and, presumably, the film - brings into the popular consciousness many facts about the Roman Catholic church that they'd rather remain hidden.
Author Dan Brown brings together a staggering array of church history and weaves a tight little story around them, often leaving one wondering exactly where the facts end and the fiction begins.
The book begins with two facts and a kind of "inverse-disclaimer":
Firstly, that the Priory of Sion is an actual organisation, a so-called "secret society", formed in 1099, which has had, apparently, amongst its members Sir Isaac Newton, Boticelli and, of course, Leonardo da Vinci.
Second, that Opus Dei is, also, an actual organisation which claims over 80,000 members worldwide. A very powerful sect within the Roman Catholic church, Opus Dei (lit. "work of God") is ultra-conservative and is rumoured to have had a strong hand in the election of conservative Benedictine XVI as successor to the relatively liberal John Paul II.
The author then goes on to state that all descriptions of "artwork, architecture, documents, and secret rituals" are also factual and accurate.
What the author studiously avoids stating is whether the little tidbits of background on the church are also accurate.
Now, I'm not going to go into detail here, because that would spoil the book and/or the movie - but there a few facts - that may, or may not make it into the movie - which might cause more than a few people to draw in a startled breath.
Opus Dei is already preparing a response to The Da Vinci Code, and has repeatedly taken great pains to remind people that the story is fictional.
(Yeah, we know that. But if I write a story about a guy who drives a Ford Mustang, lives in Tampa, Florida, and shoots people with his H-K PPK, does the fact that it's fictional mean that Mustangs, PPKs and Tampa, Florida do not, in reality, exist?)
The book is outstanding, and it's amazing to be able to go send Google off to find actual pictures of the buildings, carvings, pictures, and places that the characters are dealing with.
And, yes, you have a choice. Either let the book spoil the movie, or let the movie spoil the book.
I've already done the former.