I saw Constantine today; it was fairly good, but then, I'm a sucker for theological and quasi-theological thrillers anyway. The plot is weak in some ways, but it moves quickly (I didn't notice any drag-time, although people more familiar with the Hellblazer comics than I might find some of the attempt to set out the background a bit frustrating - there's a lot of background, and the movie is aiming to interest people who know nothing about it, so they cut corners and splice things together and simplify things down). As comic adaptations go, it's one of the better ones. It does move the scene from London to LA, and makes Constantine an American, both of which are perhaps not ideal; but in some ways Keanu Reeves was actually a fairly good choice for the overall character (it could have been much worse, and would likely have been), and I'm fairly sure trying to put Keanu Reeves in London, speaking a British accent, would have been disastrous. It could have been played more bitter and anti-heroic than Reeves does, I'm sure; but as Hollywood goes, it was quite good, and (as far as I can tell from my very limited acquaintance with the comic) was probably as close to the original as the screen could seriously take.
The allusion to Jude 9 toward the end was quite clever, much cleverer than one would expect from Hollywood (so much cleverer that I wonder whether it was accidental!). One of the clear marks that Gabriel has overstepped his bounds is that he says, "I will smite you for His honor"; a sign of (doomed) presumption that contrasts sharply with Michael's wiser move.