While the architecture itself is improving with age, I just love that so many modules have followed Drupal's concepts and have added API hooks all over the place. For example, in the new Panels 2 you can export panels to files then set them up in a module with e.g. a default_panel_minis hook to have them automatically loaded. This allows you then to develop complex views and panels locally, push your module to the production server and have the new views and panels automatically show up - pure awesomeness! More details on how to do this later in my ongoing series of Drupal rants & tutorials.