You don't need to constantly think about exactly what you need to see. Nor do I need to fiddle with arrangements. There's less fiddling. With the WM I use every window is available in every frame and I can just cycle through them. I don't need to remember what a window is called or distinguish between 5 nearly identical thumbnails because I'm cycling through the windows at full size instead of looking at list or expose. I don't need to think about what monitor some window is on or what virtual desktop and there's never any visible clutter or noise because anything that's not something I want to look at is just not visible.
