At WWDC, I listened to Apple representatives make some excellent points about taking the time to build a 100%-compliant Aqua application, and I think all developers need to look beyond the code and listen to what the folks at Apple have to say

Not quite as entertaining as Shrek, but Dock animation can be an important and useful function in your application. For example, Dock animation is a helpful way to indicate the status of your application.

Adhere to File Locations. Make sure that when your users save documents, your application knows where to put them and also gives users flexibility.

Due to the positioning of the Dock, remember that when you build an application, you have to be sure that new document window sizes and positions do not violate the Dock's space. Dock is temperamental and Dock loves his space. If you default to a window size that expands behind the dock, users will have a difficult time reaching the navigation and resize areas at the bottom of the screen. I can personally say that more than once I have been rather peeved that I couldn't get to an area of the window to resize because the default window settings always pop up behind the Dock. In addition, the new Dock in 10.1 will allow users to position their Dock location on either side of the screen as well.

If an application is designed well, the reward for users is that they will learn it faster, accomplish their daily tasks more easily, and have fewer questions for the help desk. As a developer of a well-designed application, your returns on that investment are more upgrade revenue, reduced tech support, better reviews, less documentation, and higher customer satisfaction. The rewards of building a good-looking Aqua application are worth taking the extra time.

Dock Animation. Sometimes animating icons in the dock can be useful in communicating the status of the system or application.

Drawers. Similar to Sheets, this is a "child" window that gives users access to items that do not always need to be present. But when do you use a drawer and when do you use a palette?

In building your amazing Aqua application, one of the most important things to consider is the Dock. There are three things your app needs to be "Dock Compliant." Now, I write this knowing that the Dock will be going through some major changes soon, but for the most part, these should still hold true.

But limit your animations to whatever is required to communicate the necessary information. Avoid annoying animations that discourage ease of use. Ask yourself, "What do I need to show the user, and what is the cleanest way possible to achieve that?" A good example is the Mail application for Mac OS X. Whenever a new message arrives, the Dock icon changes appearance to indicate a changed state.