Old OS X versions
Andreas in Emulating old OS X versions with QEMU:
It's weird, because I never used these systems back when they were new, and yet I feel somehow nostalgic for them. I don't know why, but there's just something about the look of them. The colour palette, the skeuomorphism, the fonts and the overall design are just beautiful, and I wouldn't mind using an OS with this kind of look and feel today.
The early versions of Mac OS X were unequivocally better designed and a preferable user experience than the bastardised offspring that today's MacOS has become. My experience started with Tiger (10.4) and I would love to go back. In fact, if someone put together a Linux distro that closely emulates the early OS X aesthetic and UX, I would finally be forced to switch.
If you want to experience the old OS X versions yourself, Andreas' post guides you through the process.