Well, there is a fundamental problem in trying to introduce styles from iOS into Mac OS X. Address Book was changed pretty dramatically to more closely resemble what it looks like on the iPad. Even third party developers have begun to "port" iOS styling to Mac OS X. An example of this is the official Twitter client which recently went on sale in the Mac App Store. It broke some fundamental UI design policies, and in newer releases the developers actually had to retract some of their decisions in order to properly follow Apple's consistency guidelines on OS X.
The main issues stems from the fact that it's honestly pretty boring to port an app from iOS to Mac OS X and contain it in a normal, bland UI window. It looks cheap. You're basically reconstructing an iPhone/iPad's screen inside a bordered area on a desktop, making it look like its sandboxed from the rest of the environment. Adding a fancy custom UI window can add some flare to it, but this isn't the right solution. Developers need to find creative ways to re-envision their apps so they look like they were written as native desktop applications, maintaining UI consistency with the rest of the OS, and most importantly, retaining most or all of the functionality that the iOS app has.
Fullscreen mode apps are a different story, though. Since there's no concept of a "window border," they can pretty much be exact replicas of their iOS counterparts.
A good example of something that meets all these criteria is the new Mail app. In normal windowed mode, it looks like a proper native application. In fullscreen mode, it takes on a different look that more closely resembles the iOS iPad app.
