SPOILERS WITHIN!
So... I'm a bit disappointed. Given Ewan didn't even bother reading the novel, perhaps I shouldn't have either. I thought the whole point of the book was the science versus religion debate - that the Camerlengo was supposed to want to give the public something concrete to believe in again. I thought that was glossed over a bit too much in the movie, so there seemed much less point to the whole thing.
But I thought it was fine, for a film of its type. Entertaining, lots of running around, ticking bomb, twist at the end. BUT... Not enough Ewan. All but one of the Camerlengo's charismatic speeches removed. The Carmelengo reduced from a psychotic fundamentalist to a misguided priest. No evil (but not actually evil) scientist... just a Nazi Swiss Guard and the Russian godfather from Eastern Promises as misdirection (subtle, eh?). The Camerlengo landing by parachute in St Peter's square in full view of everyone, completely ruining the point that he was supposed to have orchastrated a miracle that would be inexplicable by science.
I wasn't too fond of the Irish accent but I thought Ewan did a good job overall. But with a better screenplay he would have had so much more to work with. No sign of that evil Iago glint in the eye either! Bah. One day someone will see the light and get him to play a real baddie.
At least we get plenty of Ewan on TV to make up for it!