Regarding Deadpool being rated R vs. PG-13:
What a lot of people should consider is film and comics are two different mediums. Sure, comics are far more cinematic than books, but they offer a leniency towards cheesiness, which can be far more cringe-worthy on film than in those funny pages. Another factor is you're interpreting the inflections in dialogue, and how characters speak. On the screen it just may flow better with a dirty word tossed in. In the comics, references have been made toward Deadpool's knack for filthy jokes, so he could finally throw a few of those out on screen.
Deadpool's power is the ability to regenerate from gruesome injuries. He gets explicitly impaled all the time on page, but since it's drawn and not photo-realistic, it passes for PG-13. Best way to display this would most definitely be in an R-rated setting.
And for Reynold's sake this should be R to get the most out of the guy. He's great at improvising, he improvised all of Wade Wilson's dialogue in Wolverine and has expressed feeling restrained when making PG-13 films due to language caps. Though he does his best anyway.
And lastly, this would be the perfect character to experiment with as far as superhero films are concerned. Break the cliches and the fourth wall. Give us something we've never seen, and I want them to have the ability to give it all they got. No hindrances. I know some people think it'd be a good idea if a PG-13 Wade got bleeped and alluded the rating, and I believe he should break the fourth wall a few times in the film, it should only be in moderation. The comics don't depend on the fourth-wall demolition and neither should the film, unless it wants to risk tiring the audience.
But this movie's getting made, and I am thankful for that. If it's PG-13, I'll be a bit disappointed, but at least it'll exist.