These two paragraphs from Aero User Experience Guidelines > Picking the Right Degree of Control for User Interfaces are good to keep in mind:

You must also watch for fringe cases—the person who uses some obscure feature twenty times a day, or the person who uses a complex application once a year and expects to produce great results. It can be hard to willingly turn away a potential customer, but attempts to include fringe cases in your target users can compromise the interface's design, to the detriment of the majority of your users.

Every product has one category of users who are so far beyond the fringe that they don't belong in the usage profile at all. These users are the product's creators. If the developers of a software product have to click hundreds of times through a screen that their actual users will see only once, they may be tempted to apply design techniques appropriate for regular activities to what are in fact infrequent tasks. You must recognize this temptation and hold your ground against it.

The one where Chris Sells reflects on the difficulty of writing cool apps without graphic designers at your disposal, especially in the new world of Avalon/Longhorn. I like to think that I'm capable of writing usable UI, but UI thats both cool and usable is beyond me. I'd much rather design under the "requirements and restrictions" imposed by an application that needs to run on a 180x180 monochrome PDA than have to design a cool-looking application for a 1600x1200 true color desktop with easy-to-use tools and APIs that make anything possible. Where do you find affordable people that are good at that sort of design work?