I love the low-light version too, but there's just one problem - when switching between the tabs on the bottom, the page does a full reload, and it sometimes flashes white before the JS kicks in and turns it back to black. Sudden flashes of white when your eyes are relaxedly looking at a near-black page is .. jarring.
To alleviate it somewhat you could make the tab changes AJAXy, or serve a different CSS file based on the choice .. or if you didn't want to persist user information server-side a nice compromise could be making the page bg colour #888 and then explicitly set up or down in the JS.
To alleviate it somewhat you could make the tab changes AJAXy, or serve a different CSS file based on the choice .. or if you didn't want to persist user information server-side a nice compromise could be making the page bg colour #888 and then explicitly set up or down in the JS.