This ComputerWorld article syndicated on Yahoo News highlights some of what I have always found to be the problem with the Windows UI.
Friction is a good word for it of course. It just slows you down.
The issue I’ve found is that although Windows, including XP and Vista, included items such as fades, transparency and drop shadows, they simply weren’t used properly. Everyone accused Mac OS X of having useless eye candy. This isn’t the case. The eye candy was there, sometimes prematurely, to help guide you to a 3D appreciation of the desktop.
In Mac OS X, menus appear instantly and fade out. The behaviour is fluid.
On Windows, menus take time to fade in before you can make a selection. Waiting for the fade-in slows you down.
In Mac OS X, drop shadows indicate clearly which window is foremost due to the thickness of the shadow.
On Windows, drop shadows don’t indicate layering, they’re just eye candy. It takes longer to notice which window is foremost. This slows you down.
This is exactly what we mean when we say Windows gets in the way.