I can't speak too much to this as its still technically NDA. But the whole font engine is rather changed. This almost looks like a leak of some NDA type material but dynamic type is actually quite cool. Additionally the "thinness" is largely not that big of a deal with the retina displays. Past that I'm not saying anything more.

It is really nice to have some... designed text that you can hook into and use that the user can control. It scales really well readability wise, I'll just say screenshots don't quite do text in ios7 justice, and it is really easy to make it more readable if it isn't to your eyes.

But I'm sure they'll always be neue helvetica haters in general so meh, whatever, use/hate what you want to.