There aren't many image editing programs that require an entire chapter just to discuss importing because few (if any) image editing programs offer the organizational power that Aperture provides within its import facility.
While Aperture aims to address all of your image processing workflow concerns, one of its great strengths is that its flexible interface doesn't lock you in to any particular work-flow. Importing is just one example of this. You don't have to perform any keywording or stacking or metadata tagging during import—all of these features are available to you later. However, if it makes more sense to you to perform these tasks while importing, then Aperture provides that flexibility.