"And so a designer has to learn yet another language for layout?"

I've pretty much had to do that already to work with Flash. That's been a pretty limiting sandbox - we've been hearing "next year is the year Flash finally goes big on mobile and desktop" for a few years now, even from my buddy at Adobe on the Flash Light team - so I'm much more motivated to pick up a parallel set of skills for something that would be actually useful in the present day for something other than web development.