Apple updated the iPhone to 1.1.1 today. While most of the buzz is around the new iTunes Store, there is a small new feature that makes all the sense in the world: double-tapping the space bar will insert a "." followed by a space. So simple, yet so brilliant.
This is a classic example of taking a use case - a user wants to compose a message - watching users actually do that - and then improving upon it. Previous to this release, they would have to type a sentence, and then tap the ".?123" key to then have to type a period, then switch back. Three taps plus one more for the trailing space just for a period.
With the 1.1.1 update, all a user needs to do is hit space two times, an a period followed by a trailing space instantly appear.
How does this relate to APEX? Simple - once you design an application, you're not done. There are several improvements still to be made, none of which you will be able to identify. Watch your users use your application. You built it for them, after all!
See if they are clicking where you expect them to, and if not, you may need to re-think your design. Look for inefficiencies, such as switching between the mouse & keyboard, and try to improve upon them. Correcting small annoyances in an application will go a long way to build your credibility, if nothing else.
Good design is never correct the first time. Apple is well aware of this, and their decision to make the iPhone so bloody simple to update proves they get it.