If any one aspect of design drives the authors up the wall, across the ceiling, and down the other wall, it is the issue of usability. We can't begin to count the number of times we have been asked to check out sites that were beautifully designed but impossible to use. When we report this back to the requester, the response is usually along the lines of, "Well I can use it. You must be pretty stupid if you can't." In this case, the designer designed for himself or herself and assumed everyone else on the planet was his or her clone.
At the other end of the spectrum is a very disturbing trend?regarding usability as a "politically correct" mantra. In this case, the final design reflects superb usability but is absolute vanilla on the design scale. These sites are sensitive to the dictums of the "Usability Police," whose chief is Jakob Nielsen.
What's needed is balance.
Maybe web designers should heed Jakob Nielsen's principles but pay more attention to Curt Cloniger's observation in his New Riders book, Fresh Styles for Web Designers. He said, and we agree, "If a site is perfectly usable but it lacks an elegant and appropriate style, it will fail."
Why does it "fail?" The reason, from our experience, is that the designer fell in love with the technology and not the user.
When the site is finished, a great way to learn humility is to actually sit down and watch a complete stranger try to work his or her way through the site. You need to simply shut up and take copious notes. By doing that, you get to watch a real live user attempt to access the information on the site. What is intuitive to you might not be intuitive to the people that have to use it.
One final point: If you are using Flash MX 2004 and Director MX, download time should be an extremely high priority. Flash developers will tell you the Bandwidth Profiler rapidly becomes their best friend. Director developers will viciously strip out anything that isn't used in the presentation, from text to XTRAS, in an effort to reduce file size and the "hit" on bandwidth.