There's a very large, and good reasoned grumbling about Apple's repeated bashing of their own HIG (Human Interface Guidelines). Daring Fireball has alleviated all of our pent up frustration as developers and users in a hilarious parody that reads like a true-to-life-made-for-TV script. The iTunes 5 Announcement From the Perspective of an Anthropomorphized Brushed Metal User Interface Theme
A short excerpt to whet your appetite and make sure you read the whole thing:
Brushed Metal: I told you something was fucked up when the new version of Mail didn’t go with me.
Mike: You’ve got a nice long-term deal with the Finder…
Brushed Metal: That two-timing piece of crap?
Mike: …iChat, Calculator…
Brushed Metal: Calculator? I’m out of iTunes and you tell me I’ve still got Calculator? When is the Special Event scheduled for the next version of Calculator? Oh, that’s right, there is none, because no one gives a shit about Calculator.
As a developer of Mac OS X applications, Windows apps, and various cross-platform and web-applications, User Interface consistency is a real bear. Apple's Interface Builder really helps alot by providing built-in guides and tools for meeting their published HIG, if not their employed HIG. However, using toolkits like WxWidgets which targets many platforms, having an OS consistent interface is difficult.
However, no matter how difficult, interface is extremely important