The point of CSS is to separate presentation from markup. This approach uses a hierarchy of divs to define presentation. If that's alright with you, may as well use tables.
So what's wrong with putting layout in the presentation layer where it belongs? As it happens, our HTML presentation layer also contains this nice, intuitive mechanism for doing layout using "tables" that works better than pretty much anything else has (anyone remember the XmForm layout widget from motif?). So explain again why we can't use them?
Sometimes I get the feeling that the CSS layout nuts still think we're living in 1997 and that all web content is written by hand. That's just not how it is any more.
edited to avoid a rant about CSS itself.