It amazes me that people with so little knowledge of notebook displays post with such confidence.
As it's already been discussed, almost all notebook screens that claim to be "millions" of colors are 6-bit displays that use dithering to accomplish the greater color set. This can lead to the "grainy" display problem when the video driver is doing a poor job dithering. Mac OS X does a great job. It's a lot more noticeable when using Boot Camp (or at least it used to be, I know it was a big problem when Boot Camp drivers were first released).
I'm totally psyched about LED backlit displays. Lower power consumption with greater brightness? I'm in!