The white paper only discusses ways in which to implement some of the main concepts, such as using categories for your @ ??? action lists, as well as how to make custom views.
On the other hand, the plug-in adds some very useful functionality, such as linking tasks to projects (also tasks), some very helpful custom views, and some automation in terms of moving emails into @ action folders, and then back out upon completion. Because the projects are tasks with a category of Projects, they will sync to a PDA. It also allows for viewing multiple tasks related to a project, something I was lead to believe was only capable doing it the Project-by-Contact method, but that is definitely NOT the case.
Having tried out the plug-in now for a couple of days, I definitely would recommend it. However, I am running Outlook 2003, and it doesn't work perfectly. Everytime I open a new email to send, I get errors, which require pressing OK numerous times. However, it does work. There are a few other tiny bugs that I've noticed, but it is worth a 60 day trial to get it up and running, and hope they get out a compatible version in the meantime.