[thatjoshguy]

Possibly the UI of iCal and Address Book might have the inconsistant UI, but they still have the exact same UX as every other OS X app, thanks to all (with the exception of iTunes?) being built in Cocoa so they all use the same text controls and menu items etc.

You can create a Cocoa app in XCode and just add a text field, and you will automatically get spell check, dictionary look-up and font controls. All your shortcuts will work exactly how you would expect them to (ctrl+a, I'm looking at you). You get a help menu with built in search of the menu bar (http://cl.ly/8yKI). All with no effort from the dev at all.

The only exception to this would be Adobe apps, but at least they have their own UI/UX that they seems to follow most of the time (but they actually hate Apple/OS X, so they probably just do it out of spite)