I've only shipped one or two little things with WPF. I think the author makes plenty of good points. And some points which I'm not advanced enough to understand.

But I actually like writing XAML by hand.

The GUI-based GUI designers I've tried were never very good about expressing the subtleties and details that you have to deal with if you hope to make a professional-grade result.

GUIs that are good at specificity and detail also tend to be quirky and difficult (think CAD systems).

The fact that XAML is so closely tied to the actual structures you're creating means you learn the language and its domain together. And you can trivially re-use or re-purpose chunks of XAML by copying, pasting, editing.