*SPOILERS*
I saw this last night, and I thought it was pretty crap. The art and production design look great, but that's about where the good stuff ends. The story is boring and by-the-numbers, Paul Bettany looks like he can't be arsed half the time, and Karl Urban looks like he gave it a go, but ultimately the poor script lets him down completely. There just didn't seem to be any sense of real threat beyond "Ooh look, a big train full of vampires", and the film, much like the train, goes nowhere.
Not to mention the fact that it's so full of shitty cliches - the little girl who turns out to be the main protagonists daughter, the former friend/comrade who was taken and turned evil by the big bad, the Church/Government covering up the truth, sending Priest's former comrades out to kill him to protect society, one of whom turns out to be his forbidden lover who betrays her orders to help him out...
The whole thing felt like a big budget pilot for a TV series, which would probably be more interesting than what we got here.
Really, they should have just made a more literal adaptation of the Priest manhwa, which has decent enough potential in itself, instead of just hijacking the name and making this shower of shite.