Here is the poster if you haven't already seen/cried over it:
First of all, I think it's STUNNING. Shailene and Ansel are really becoming Hazel and Augustus in my head now, which is exciting for me. I also love that they kept the same font and colors as the book cover, and this picture will look great on the movie tie-in edition of the book which will undoubtedly happen before the movie comes out. And I also really like the fact that Hazel's cannula/oxygen tube is featured on the poster. They didn't try to "pretty up" the plot and smooth over the fact that she has incurable cancer. I think that says a lot, especially in a culture where we photoshop perfectly beautiful people before we feature them on magazine covers.
The main thing a lot of people have a problem with, though, is the tagline: ONE SICK LOVE STORY. I admit, I cringed when I first saw it and had the, "Really, Hollywood? Cancer puns? Really?" But then I started thinking about it, and John Green posted his opinion on his blog, and I understood. The sarcasm is in the same vein as Hazel's narration. She and Augustus and Isaac joke about their cancer throughout the book (Hazel says her lungs "sucked at being lungs," for example), and they all have a dark humor about them.
I think the tagline would be something that Hazel would say on a whim, and Augustus would grin (his real smile, the one too big for his face). I think the two of them would like the tagline.