As you suspect, it would need a long answer. Remember that Peter's book focusses on a best-of-breed solution involving more than one application - it's Bridge (a folder browser) plus iView (catalogue with folder management), and advocacy of the DNG file format. Aperture's aim is "one ring to rule them all".
People obviously get it working to their satisfaction, but from a DAM Book perspective I'd throw these at you to think about:
- You lose control of your own folder structures. The bucket system means that if (when) something goes seriously wrong, you only need low level Finder/Explorer folder skills to reconstruct your archive. Aperture only works with virtual sets (its projects correspond to iView's catalog sets) and obscures the real folder locations, so for a reconstruction you're dependent on Apple having thought of everything and on you understanding how they want you to do it.
- It won't write metadata (either descriptive metadata or adjustment instructions) back into a sidecar next to the original or into the orginal DNG, or update the embedded preview.
- It won't read xmp sidecar files
- It's a single platform solution.