I recently booted up my old Mac and installed Mac OS X 10.3 Panther on it. It brought back memories and made me remember why I was so drawn to Mac OS X back in those days: everything looked amazing.
I enjoy reminiscing over old user interfaces. GuideBookGallery (external) chronicles how operating systems evolved over time with an impressive collection of screenshots.
A quick comparison of what about eleven years has done to Mac OS X (Panther was released in 2003, Yosemite in 2014).