Yeah i admit that i haven't used used mac os x much, well it should add up to like 3-5hrs overall. I know thats not much, but enough to feel the distinctive feature of mac os x: one menu for all windows. It's not bad thing, saves vertical screen space. But i don't like it because there is totaly no way this could be used with focus follows mouse, witch i consider more useful feature. Now even more personal thing, after like 2 years of using focus follows mouse, i decided to disable "click rasess" (that means that window can only be rased by clicking on border/titlebar or in a task bar) at first it seemed a little "WTF" (i had the same perception with focus follows mouse for first couple days when i tried it) but then i have seen how useful this is, especially if you have to copy/paste a lot.
Of course i understand that such thing like focus follows mouse are for more advanced users only, computer newbies are confused even without this, and if they would have to always look where the mouse is i think it would be much harder for them (although skill gained by this should be useful later on i guess).
Id say we can split all users in 3 categories:
newbies or low users, who use one app at a time, for them there is totally no difference in usability be it Windows, Mac OS X, or one of *nix/Linux WM styles, they have one window and are happy with it; Second group would be someone who use few apps at a time, i'd say 2-5, then the best thing for them i thin should be multiple desktops, switching between desktops using hotkeys is WAY faster and more intuitive then hunting for windows on task-bar or dock; And then heawy users, like me sometimes, i always have 8 desktops, and sometimes several apps/windows per desktop. Then focus follows mouse and tabbed windows should be better than mac style menus.
One type of apps that would GREATLY benefit from tabbed windows are instant messengers/skype. Such app have main window, and then window per chat. If your talking with several people, then task-bar and alt-tab becomes very cumbersome to use, but using tabbed windows you can manage skype/im apps windows very nicely and neatly. Same goes for browser. if you have a lot of tabs you might one to have another window, and it you can tab windows it's very nice hierarchy, same for terminals, text editor when programming etc.