I've always wished for the whole ENV: & ENVARC: thing in Windows / Linux.
It's nice to test changes in a temporary fashion without commiting them to the registry or home folder. A quick reboot and the size 30 Opal as your main font making your windows too big to change back was gone. I know in modern OSs you wouldn't want to reboot after every minor change but a simple "reset to stored settings" option would be nice.
I also liked how you could back up all of your settings just by copying the envarc folder to a different location and imporrt them back after a reinstall.
The Linux way is better that the horror that is the Windows registry but I think it's messy having loads of .blah folders in your home directory that can quickly fill any selection dialogue windows you have open.
The general structure of the OS was easy to learn and understand too. C: Libs: etc etc all made good sense and are far less confusing that Windows or Linux.
