Questions (spoilers)
Well, since I read elsewhere that Camerlango had planned to have a vision of where the bomb was at the last minute, that clears up THE major plot hole (i.e. how he could possibly expect, excepting great luck, that things would possibly turn out the way they did), but I'm still left with some questions:
1) Where are the Illumanati? If they have infiltrated the Vatican shouldn't they have been working behind the scenes to stop Camerlango? After all they'd be like "We're blowing up half of Rome? Isn't that a terrible idea? No, we're not? Then, since we know where the path leads why don't we just come up with an excuse to wander along, spot the bomb and go 'Whoomp, there it is!'?" Does that mean that in Dan Brown's universe, the Illuminati are either extinct or less competent that they are credited with being?
2) Why was Robert Langdon gifted with Gallileo's tract? After all, the only information about the Illuminati in it was the poem about how one could find the path (and therefore get initiated into the Illuminati), and he already had that. And it's hardly something that would make for an entire volume in a 2 book series. And, regardless of what that vandal Vittoria said, it would only take less than a minute to write that down on a piece of paper. Shouldn't the Vatican keep that tract under its care where they can keep it more professionally preserved and make it available to, say, someone who was actually writing a book about Gallileo?
3) If the path is pointed out by angels and demons, where were the demons?
And, no, I'm not taking the film too seriously. If I was, I'd be ranting about either its poor science, or treating it like a serious treatise on religion or history because it can supposedly turn Christians into atheists (or vice versa -- atheists often prove to be as moronic and prejudiced as they rightly or wrongly accuse others of being), or give people who are blissfully ignorant of history some different misconceptions than what they already have.