My original intent with More Power to Firmware was to put up some sample Forth code for doing graphics with mouse input in the Open Firmware implementation that Apple uses. I have included a discussion of the Extensible Firmware Interface (EFI), broadening the document's scope.
Three complete (though prototypical) examples are included: Towers of Hanoi (textual) for EFI, Towers of Hanoi (graphical) for Open Firmware, and creation of a mouse-draggable window for Open Firmware.
The performance of computer hardware typically increases monotonically with time. Even if the same could be said of software, the rate at which software performance improves is usually very slow compared to that of hardware. In fact, many might opine that there is plenty of software whose performance has deteriorated consistently with time. Moreover, it would be rather difficult to establish a single (or at least objective) performance metric for software as complex as an operating system: a "faster OS" is a rather subjective phrase.
Making An Operating System Faster provides a sampling of things that Apple did (beyond initial/fundamental OS design and implementation) to make Mac OS X "faster".