Short bio: Computer Scientist, FOSS supporter (read more)
Tux Machines (TM)-specific
I've been fortunate to use a pretty wide range of OSes over the years -- some by choice, others by necessity. I'm no fanboy, but some of those systems left a better impression than others. Almost every OS, though, has something about it that's unique or revolutionary or just helps you get the work done and on to other things. And sometimes a feature of the OS just grabs your attention and forces you to dig further, understand how it works, and master all it can do.
Each OS has some nugget that we can enjoy, learn from and build on. So here, in no particular order, are 10 different features I love in 10 different OSes.
Mac OS X, Time Machine
Configuring backups has, traditionally, been one of the least fun things about computing. It's perhaps only slightly less frustrating than trying to recover your system from said backup. If you don't have too many files to back up, services like Dropbox, Sugarsync, and Windows Live Mesh work quite well. In fact, for several years I used Live Sync (formerly Foldershare, now called Live Mesh) to create real-time offsite backups of my most important files. But you can't back up and recover an entire system that way.