Need a GUI.
Why is this a weakness?
My company uses our portal to generate the XML code. for our RSS Feed. We have complete control over the interface.
We also have a basic spell checker for input and because the code generates the XML we have no need to check for syntax upon build (it complies with the schema).
Also, RSS (as far as I know) was not design to create high-end applications. Why would you want to complicate something that is so simple? That's like saying you can't build an commercial aircraft completely out of syrofoam even though it makes great toy planes.
I like the rest of the article... I hope to see more details in later versions of it.