In the iPhone HIG, there's a section on bringing a desktop application to iOS[1]. The entire HIG spends a fair amount of time talking about the different needs of mobile and desktop users. Until Apple releases a document tailored for them, any iOS developers who are planning to port their app to the Mac might want to reread the HIG, this time looking out for what's expected from a desktop app.

[1] http://developer.apple.com/library/ios/#documentation/UserEx...