This is something I don't understand about these sorts of grid systems. Isn't using specific classes for the divs of the grid in the HTML just as difficult for maintenance purposes as using a table? You're defining specific rows and columns and because you're doing so with class names, that layout information is in the HTML and not the CSS.

The point of using CSS for layout is to have the markup be relevant to the content of the document, not for it to be relevant to the styling. Just as having class names like "blueText" or "thickBorder" is injecting style information into the HTML, so is having class names like 'g80' or 'g940' or whatever.