Granted, for many users, speed matters. But, here are some other concerns.
1) The Registry File. Enough said.
2) Under OS X, open any kind of file in any kind of editor. Go back to the Finder window, rename the file, move it to a different folder no problem. Can't be done under Windows. Half the time, even after you close the file (not the editor app), the app fails to 'release' the lock and you STILL can't rename the file.
3) None of Microsoft's pseudo-shell implementations come close to bash/csh/ksh in useability.
For most users, most of the time spent on a computer is in dealing with the UI/GUI/UX (whatever you want to call it). That's what matters; raw speed of calculation is the primary need of a rather small subset of users (who probably buy time on a cluster node :-) )