You can disable each feature independently if you'd like. Conversely, cover the camera hole and the backlight will turn on and the screen will dim. Shine a bright light into that area and the keyboard backlight will turn off and the display will brighten. The ambient light sensor is built into the camera assembly in the Air's bezel. I lived without the backlit keyboard on last year's MacBook Air, but I always missed it. The backlight functions no differently than in the MacBook Pro and is very useful for those of us who do a lot of writing at night. The 2011 models go back to their 2008 roots and both have a backlit keyboard. You knew as soon as people started complaining about it last year that Apple would have to return to a fiber optic backlit keyboard in the next MacBook Air.
