Charles Petzold talks about XAML on his book blog. (He's writing a new book on Avalon (aka WPF)). While he believes that XAML makes sense as an alternative (his emphasis) to procedural code, I think it's an excellent first choice. It's easy to stub out your UI with XAMLPad or Sparkle, then wire up the bits in code. You can make changes, move this button here, add more whitespace to this grid, then view it, tweak it. This isn't that easy in C#, code, run, look (doh! move that button over one pixel. rinse lather repeat). However some people may miss the bigger point here. In Avalon, (aka WPF) you can layout your UI however you'd like. I think that Sparkle will definitely bring more people to the XAML side of the fence. Now if I can only get my hands on Sparkle. And please do take a look at "The Two APIs" on Mr. Petzold's blog.