Someone should license AmigaDOS and make an X Window manager which is as simple, elegant, intuitive, and resource-thrifty as AmigaDOS on (free)Unix. If it can be usable on a 7 MHz m68000, then it's doing something right. If a 2 GHz+ machine with hundreds of megabytes per second of throughput to a video card can't keep up with a human, something is horribly wrong. This is why I won't ever use KDE or Gnome again unless I hear something has significantly changed - they are not intuitive, they are messy, and I don't feel like wasting my cycles, both in my computers and of my own time.
All of my GUIs these days are Mac OS X. It's certainly not perfect, but at least it does what it's supposed to do in a meaningful and understandable way.