What would really help would be a computer screen that used natural light, right?

Yeah. You could use it in bright ambient light and attack SAD while computing.

It's on the horizon. A friend of mine recently bought an electronic book device that I'm told uses the new-fangled electronic paper -- a kind of surface containing oodles of tiny little spheres that are black on one side and white on the other. Electric fields turn them back and forth, and you get a screen that is seen be reflected light (so the brighter the ambient light the clearer) and uses power only when the image changes. It only does black and white and grey-scale, but I suppose it should be possible to make something like it as a computer screen.

I suppose that device is, technically, a computer with the screen, but that's not how it's marketed. sps tells me that it's possible to reflash with Linux, but that that voids the warranty. Another example of a manufacturer that doesn't know that the way to harness the power of free software is just to allow it, and to publish hardware specs, which they already have to have in-house anyway.