Pixelmator, while a very nice image editor with layers, healing brushes, lots of effects, filters, etc., fails as a scanned image editor immediately because it has no separate control for each channel when leveling. Seems a big miss to me, but perhaps I just haven't found the right tool.
Similarly, Aperture fails immediately due to the inability to invert images (there is apparently a hackish way to do it with the curves tool, but I couldn't make it work).
Good thing I have PS Elements packaged with the scanner...