Jonah Hex is just another comic book that I don't know anything about but the casting news that appeared on the net today is big for the film that Warner Bros is funding and distributing. 

A trusted source tells Hollywood Elsewhere that Josh Brolin has signed to play Jonah Hex which is directed by Mark Neveldine and Brian Taylor.  "I'm told that the deal is sealed for Josh Brolin to star in Jonah Hex, based on the graphic novel..." Jeffrey Wells writes.  "Brolin's rep is not only denying this but claiming Brolin is 'not attached,' but a voice is telling me to consider the word of a friend who tells me the deal was locked down last night."

So as of right now, I'd say treat this as a rumor until it's confirmed by either the studio for the trades. 

Considering that I don't know squat about Hex, I think it's safe to say that whatever Brolin gets casted in is a good thing.  He is after all a very good actor.  The early buzz for "W" in which he plays President George W. Bush,  is very good.  Most say the movie isn't that great but Brolin himself is excellent as Bush.  Even from the trailers of his new film, I'd say that he did a great job.

We'll find out within the next couple of days, I'm sure, if the news is true.  I'll keep you updated but until then it should be treated as a rumor.

-Phil