I tried to look more carefully at someone using a mac today, seeing exactly what was slowing them down, and I think I've got it. See, macs have their menu bar at the top of the screen as opposed to on the window (this is not a bad thing, just different). However, modern applications come with more than just menu items. They generally have status bars, toolbars, tabs, etc. These appear on the window itself.
So now you have two potential places to click around on: the top of the window and the top of the screen. In order to get their applications nicely centered on the screen, mac users often have to click and drag to resize their application. A lot of the resizing happens due to the users trying to click on something at the top of the window, and looking at the status bar at the bottom.
Now the reveal:
First, move the status bar to the bottom of the screen, not the window. This way switching between applications changes the status bar, switching between windows keeps the status bar in the same viewable place. Do the same thing for toolbars, but at the top, as if it were a maximised window in Windows. The downside of this approach is that there's a lot of screen real estate used by default, but with clever auto-hiding and information "squeezing" there's no reason this can't take as little space as it currently does. The big advantage is that the toolbars are always there, where they're accessible. You can click on toolbar buttons for an application without being able to see the entire window / the top of the window / etc. A lot of the resizing that currently occurs should be minimised. If the mac panels are anything like gnome panels, you'll be able to place them anywhere around the screen (like the left or the right) for a flexible setup. The second advantage is that each window, where these controls are duplicated, get a lot more screen space to display everything.
Second, get rid of the scrollbar on document viewers. Scrollbars really don't take advantage of the fluid window management in the mac. They also limit the power of the scroll wheel. My proposal is that the window grows to the size of the document (at least, perceptually). If the webpage is 1000 pages long, the window grows to 1000 pages long. In order to "scroll" down the webpage, you have to move the entire window up or down. Now you can use the scroll-wheel to move actual windows around. Modern scroll wheels are two dimensional, so this makes manipulating windows very easy. Easier if you add IE-style auto-scrolling. The big downside is that now you can't completely control the size of certain windows, but I see more mac users size windows to what they would've been with the above implementation than to some other size.
Finally, get rid of the title-bar. The only real reason for the title bar in a mac is for shading and moving a window. Because window movement can now be done with the scroll wheel, the major purpose of the title bar is gone. It takes up room, and it makes the top of the window more important than the rest, which is clearly incompatible with the "windows move everywhere" philosophy above. Get a key combination + middle mouse button to shade. This way middle mouse button + scroll wheel + autoscroll can control all window motion. A window should shade to where your mouse is, and re-expand to where you left it. This allows users to shade docs out of the way when they're doing other things.
I'm thinking this is a good idea. What do the mac users think?