Joel Garreau's Nine Nations of North America is still enjoyable, particularly because it is not nearly as dated as you might suspect. I was given it as a gift in 2001 and read it expecting Garreau's fieldwork to show me how people in North American regions used to talk. However, much of what Garreau heard and felt as he traveled accorded with things I'd heard and felt in my travels in the `90s and `00s. The only thing that struck me as (semi-)dated was Garreau's devotion of a significant portion of each chapter to how that "nation" was facing the energy crisis. Is such a concern really dated, though, given how the intervening years' explorations and exploitations more or less tabled the discussion for a future date?
As the holder of a B.A. in Geography, I winced at his choice of the word `nation' when clearly the better term is `region'. Nations are not defined by their interests and way of life, but rather an elusive mix of shared histories, cultures, and socio-political happenstances. However, Garreau's work serves to remind geographers that regions are indeed best defined by interests and way of life, despite much attention given to religious or institutional commonalties (i.e. "civilizations") recently.
What do I think of Garreau's boundaries? Let me answer this way: my brother-in-law recently remarked to me that in trying to correct misconceptions his fellow students at Harvard have about the Midwest, he'd explained that he felt Michigan was a lot more like Pennsylvania (typically considered a "Northeastern/Mid-Atlantic/East Coast" state) than it was like Kansas (often grouped with Michigan as a "Midwestern" state). I laughed and handed him Joel Garreau's Nine Nations of North America. That myriad others have made similar observations I do not doubt. This is the service of Garreau's work: a corrective to our customary understanding of how North America is broken up.
Do I buy into Garreau's boundaries, though? With some minor amendments, yes. I agree that Manhattan, the D.C. area, Alaska, and Hawaii are "aberrations" and would add Central Florida to that list, or perhaps move it into "The Islands", but it is clearly no longer part of "Dixie". A more minor quibble I have would be to shift the northern boundary of the Foundry into Lake Superior rather than splitting the U.P. with "The Breadbasket" (no way Copper Harbor or Marquette is a "Breadbasket" town). If I knew northern Wisconsin better, I would say Superior and Wausau are more likely Foundry towns than they are Breadbasket; that's my suspicion based on the fact that that area is woodsy, rugged, and pocked with mills and factories, and thus perhaps not as concerned by the fate of agribusiness as Kansas City or Minneapolis is.
One last and funny (but not "ha ha funny") thing is that Garreau, in trying to circumscribe New England, notes that there's significant French population along the northern tiers of Maine and New Brunswick, and if it were not for the absurdities of political borders, would put them in with Quebec. However, one thing that characterizes New England (and that perhaps he misses) is its history and culture of significant French influence, from Nova Scotia to Rhode Island.