Debian Woody > Red Hat 7.0 > Slackware 9.0 > Slackware 10 > Debian > Ubuntu > Mac OS > Ubuntu > Arch.
At least for desktops and laptops.
For servers I'm still primarily running Debian (and one instance I'm running Arch).
The reason why I settled on Arch is primarily because the combination of bleeding edge and being stable enough for daily driving it. The AUR also adds sooo much, that there is nothing I really don't need to manually install anymore.
For servers, I basically want a rock stable system. Hence why I've chosen Debian Stable.