Ever needed to work late at night or during a night travel on a car backseat? I did, and I felt like the default Clearlooks color scheme was attacking my eyes.
I used the Mist theme and simply changed a few colors (that you can modify yourself if needed), to make them dark enough to not emit a "light halo" in the car, while remaining "usable" (tested with Evolution, Tasks, the Web, etc.). This theme is therefore aimed at reducing eye strain for low-light environments. It also provides you with a scary "hacker-looking" laptop so that people can wonder what the hell you're running as an OS, I guess :)
I chose the Mist engine because it is the fastest engine out there. You wouldn't believe how much that thing makes a difference until you compare Mist and Clearlooks for scrolling webpages in Epiphany (or Firefox). Or the speed that it takes to draw windows.