Great article, thanks for this 
As for the comment about css being so easy to learn that it can be done over a weekend, it really depends what do you mean by ‘learning’. If you mean to be able to do something with it, sure, you can even create your first layout just after having studying css for a few hours.
Now, how about making it cross-browser compatible and responsives ?
How about smart layout that adapt to the content, and doesn’t break as soon as the content is not exactly ‘ideal’ for your layout ?
How about knowing exactly how to combine the different properties ?
Does width: 0 auto works to center horizontally a div without a fixed width ?
How does percentage actually work ? it’s a percentage of what ?
How does background-position work ? does background-position: 25% 25% means the left and top edges of the image will start at 25% of the left and top edge of the div ? No it doesn’t.
Knowing the details and how to combine css properties take time and is definetly not learned over a weekend.