I imagine 99% of the people who see it won't have a clue what Hellblazer is. I don't read comics, have no interest in reading them, and it looks cool to me. That's probably indicative.
Finally watched the trailer- ick. Apparently the marketing people couldn't decide whether this was supposed to be the Matrix or Van Helsing (the answer, of course, is "neither"). And was that some sort of gold-plated chain gun he was carrying in a couple of scenes? Things were moving too fast to tell...
Well, I have good news, good news, and horribly bad news.
Good: Here's a picture of the person playing Gabriel. Although it's a woman, it looks just like him.
Good: Here's a picture of the woman playing Ellie. Looks just like her.
Bad: Chaz Chandler, Constantine's best friend and a taxi driver, is being played by Shia LaBeouf. Shia is a good 18 year old actor, but inutterably wrong for the role as we know it.