The Cocoa documentation was completely redesigned this month. Class docs are now whole sections, rather than a single page each, and each such section now has the same look and feel as a Carbon Manager's docs. Check it out:
My favorite feature of the new design is that the class names are no longer in two columns. The two-column design was theoretically a good idea, because it meant that the page was shorter (which would ordinarily mean less scrolling), but bad in practice because it means you have to look in both columns to find a class (especially if its name is near the middle of the alphabet, like the NSMutableFoo classes are — there were some of those in each column in the old design).
You can copy these docs to your own machine by going to Xcode's Preferences, Documentation pane, and clicking “Check Now”.