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Expose is pretty similar to that. I have it set as F5 on my comp. It displays every window in a given application. There is also a function to display all open windows in every app (F3 for me).
 
Expose is great. I use it all the time with the top left corner of my screen set to show all windows. Zip my cursor up there and select what I want. But with something like window tabs, all selected windows are locket together and moved together, each tab represents a window, clicking on that tab brings that window to the front. And you can drag and drop between tabs / windows. I like the look and neatness that it provides. I'm kind of a neat-nick with the open windows on my desktop so I keep them stacked on top of each other and centered on the screen. Window Tabs would do this for me.

I've asked the creator about a Mac version. No reply yet. If they don't made it, someone will.

Thanks
 
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