If you have been following along, he has posted the next part (part 5) in the series.
http://t-machine.org/index.php/2009/10/26/entity-systems-are-the-future-of-mmos-part-5/
FINALLY!!! 
I’m actually right now starting a project that will implement a similar solution. Seems like what he posted is what I was missing.
Seems very interesting. Some bits are hard to visualize without actually having a game to develop with it, but it seems like it would be fun implementing the entity system approach. Could be done in a very reusable way too.