Read it. Hated it. It was as simple, repetitive and ridiculous as a Dr. Seuss book. And Dr. Seuss does it much, much better.
All this talk of historical accuracy/inaccuracy from a scholarly standpoint isn't really the issue, as far as I'm concerned. What concerned me the most about this book was the way it unapologetically took a religion and lied about it, then mocked its adherents over and over and over. I have nothing for or against the Catholic church, but if this book had been a historical fiction where the 'scholarly' protagonist had copious (fictional) evidence that the Holocaust never happened, or that the 500 year bondage of Africans wasn't really all that bad, or any number of 'sensitive' histories, he would have been pilloried. He took a very big, very timely target and raked it through the mud supported mostly by the pseudo-science found in Holy Blood Holy Grail and other silly sources. So, all those people that don't know the Dead Sea Scrolls from the Bhagavad-Gita can now wander around quoting from Brown's 'scholarly' work about how vile and twisted the Catholic church (and by extension Catholics) are.
Aside from that, it was just execrable fiction.