I am somewhat prone to using my computer late at night.
Sometimes, this is before I go to bed. Other times, I am “oncall” for a service and get woken up at 2am, 4am, etc and then need to be able to get back to sleep after dealing with an issue.
The best change I've made to accommodate this? Installing f.lux, which has binaries for MacOSX, Windows (7/Vista/XP) and “Linux” (by which they mean Ubuntu). [No source, as far as I can tell]. This gets your timezone, figures out what time the sun goes down and comes up and gradually changes the colour-tone of your display, to be much less blue and bright at night.
It's not a gimick and I am less prone to staying up until 7am with this installed. Colleagues report similar results.