According to
Anderton it is better for the waveform not to change but I don't agree with
Craig on this at all. Studio One also alters the waveform height too and yes it IS very helpful. When you are practiced at it you can match rms levels almost perfectly by eye. It saves much time.
In Sonar you have to render the changes into the wave before the height of the waveform changes but I think that it slow and cluggy. In most other DAW's the waveform height is reflected instantly and personally I think it is a great feautre.
You can almost get a perfect mix just using clip gain alterations for example. It is cool to be able to modify levels of individual audio clips like that and see the result too.