Macromedia Flash MX is great for building good looking custom UI, but most of them simply sucks when it comes to interactivity.  Using Flash-based UI feels like you are doing it underwater and behind an inch thick glass.  Controls feel sluggish, oily, and unreal like they are not really there.  I suspect this is due to problems with how Flash manage events and threads.  There might be ways to make the components more responsive using ActionScript, but its not apparent.  I am gonna experiement for a few more hours before the night is over.