Typical uses are recording, e.g. a vinyl record say. Also equalizing the volume for a set of tracks, something that is often required for a compilation. The noise reduction tool is clever, you get it to 'learn' the noise from a sample of what is supposed to be 'silence', then have it find it and remove it from the recording.
Edit: PS does waveform and spectral view, zoom in (until you can see the actual sample points, and even move them about!) and has a spectrum analyzer window. Loads of filters and things including 'silly effects'.
Re Aerial, I can very easily make a single disc compilation of the bits I like most. Haven't done it yet though.
