What regions do you find most overrated and underrated?
I'd say:
Underrated: The Midwest. Very livable, weather is not as bad as people think (spring and fall and often summer are very nice), fairly friendly and ethical people, surprisingly diverse. Lots of water. Not necessarily my favorite region of the country but it doesn't deserve all the flack it gets for being flat, backwards, ignorant, etc.
Overrated: The West and Hawaii. Expensive, too car-centric, lack of a distinct culture aside from Mexican and generic US culture, large swaths of the land are unsightly, not as friendly people as the rest of the country, weather is a bit too hot and/or dry (or cold in the inland Northwest/Rockies). However, the national parks DO live up to the hype and are amazing.
Rated about correctly: The South and Northeast. Lots of advantages and drawbacks alike to these two regions. The South has an awesome culture but crappy workers' rights and overall just too conservative. The Northeast has a good political culture and public transit but is too expensive on the coast and too few opportunities in the interior regions like Upstate NY and Vermont.