Chad Nevett is spending 24 hours writing about "Hellblazer" during his blogathon to raise money for the Comic Book Legal Defense Fund. As I type this, he's halfway through, and if you want to follow along (or see what you missed) go over to GraphiContent right this very minute!
I've only read about 1/3 of the stuff Chad's writing about. I read almost all of the Delano issues, and then I ended up abandoning the series in the middle of the Garth Ennis run, which is widely considered the high-mark on the series. I just didn't care about Constantine at the time, I suppose, but I should go back and reread all of that stuff, and pick up the Ennis issues I missed.
I do like the bits of the Azzarello run that I've read -- which is basically "Hard Time" -- and I bought that for the Corben art. I said it on Chad's blog and I'll say it again here: Richard Corben is the best artist to ever work on "Hellblazer," and he's had some seriously stiff competition. But he's Richard Corben. And he got to draw a Constantine-in-prison comic.
Blogathon! Go read it. And support the effort.