I particulary like their technique of encapsulating a WebPartManager and other links for switching between Browse, Edit, Design, Catalog and Scope mode of Webparts, into a User Control and then re-using it across entire website through dropping it onto Master Page. This control intelligently checks if the current page and user is allowed to switch to another mode and then displays the appropriate links.
I also liked their File-based storage approach instead of using SQL Express for storing personalization data of the Portal Framework, although not suited if in case the portal has many pages and many users. (See the App_data folder under the application root folder, it stores information for each user on each page, therefore its not very scalable), but is a good example of using a custom provider.
I wish if the article also included Connectivity between different Webparts and displaying data in one webpart based on the selection in other webpart.