"HTML 4 is far better for laying out text than anything in Silverlight or WPF"
One bad e.g., in HTML, if you have a 100x100 div, with a span inside it with a loooong Url as text, the Url/text doesn't break to fit inside the div, it just stays on one long line.
Actually, I've overstated that complaint in the case of WPF because you do have the FlowDocument there - not as powerful as HTML, but useable for most scenarios.
Silverlight however is as basic as VB3 for text layout - text is just formed in rectangles. Want to wrap it around an image, or any other content? Forget it. The RichTextBox added in SL4 allows for some styling, but you still end up with just a RichTextBox,
like old-school VB. And the styling system of XAML, while good for laying out controls, is both cumbersome to use and not as powerful as CSS when it comes to laying out content.