There is more than one option. I have started separate thread in favour of OSes in general. Though I have a Mac there are many that will do. Mac is most famous for its GUI, but I often do not use a GUI. On Unix and alike I also run the X11 GUI with Twm as it allows me to work from more than one window at a time as focus is separate from raise. Neither Mac nor Microsoft can do this.
For example I will raise a document window over an edit window and then focus on the edit window when writing code.
Often I only need have the bottom of the edit window visible.
There are also important privacy and freedom issues. See OS Wars and Warfare:
http://sci.rutgers.edu/forum/showthread.php?p=1210854