Self-Illumin/Bumped Specular shader change in Unity3

I just upgraded to Unity3 and noticed that the Self-Illumin/Bumped Specular shader had changed a bit as the Illumin got it's own area in the Inspector as it's now required to have a separate texture for the illumination maps? (It used to be in the alpha of the normal/bump texture before).

Now, I wonder if anyone knows why this was done, as the RGB channels are going to waste on the separate illumination map as it's only using the alpha, isn't it? At least, I couldn't see any difference by playing around with the RGB channels. Would be great to know how to take proper advantage of this. Thanks! :-)