So having been through a small but not insignificant portion of the US, I thought it would be a good time to give a running assessment of what I thought of each area, in very broadbrush (aka totally unscientific and probably biased) terms. I will be doing this periodically, for the sake of brevity, doing it by state.
California - Not much to say about it that hasn't already been said really. The best observation is that if you want to experience a little bit of every other state, go the California. You'll be guaranteed to find something there.
Oregon - The last bastion of the true hippie. I'm not talking about the Burning-Man-going-pot-smoking-lives-at-home kind of hippie but the brown-clothes-backpack-dreads-wandering-aimlessly-communing-with-nature kind of hippie. They seem to exist everywhere there, and are more or less tolerated as a feature of the landscape, like say... the bums of Berkeley.
Washington - If there was a state that resembled California, this would be it. The coast definitely has a bay area vibe, albeit with a bit more of an outdoor emphasis. The interior is surprisingly dry and the eastern edge hits the Rockies and thus goes back to being woodsy, not unlike a larger version of the Sierras. You also get your spectrum of people from the progressives of the coast to the bible-thumping conservatives of the central area. I can see why bay area transplants do so well in this state.
Idaho - Umm... Potatoes? I saw about 2% of that state, and nary a potato I saw...
Montana - A surprisingly pleasant place to be. Yes... it does get bitterly cold in the winter, and you are well... far from practically everything, but at least it isn't Wyoming? I mean, I did see a Japanese student with her parents at the University of Montana, so that's got to count for something right?
Wyoming - Yellowstone aside, Wyoming is probably the last place I'd want to be stuck in. Think of it like this: Picture the Mojave Desert. If you can't, picture the Sahara, but with some random shrubbery and some cactus. Now take out the cactus, and cut down the shrubbery. Then take a giant rolling pin and flatten everything out a little bit. Finally, throw in a road (maybe two, if you're really adventurous) and a power line. Voila! You have Wyoming. I have serious doubts as to whether people actually live in the state or they just stick random buildings there to keep the tourists happy.
South Dakota - Another surprisingly pleasant place to be, after the barren wasteland that was Wyoming. Scorching temperatures aside, SD has its share of national parks, and at least there is either a)Signs of civilization or b) wilderness, not this strange limbo land of fenced wilderness like I saw in Wyoming (I think you're starting to the picture of my feelings toward Wyoming). Just don't go to the capitol (Pierre). That was quite possibly the biggest dump of a city I have seen, and I had to check multiple times to make sure that it was in fact the capitol instead of say, a really bad wrong turn into those areas your parents told you never to venture into.
North Dakota - So far this is the definition of a "Meh..." state for me. Its got the sparsely populated look of SD without any of charm or major national parks. On the plus side, its capitol is actually a decent city and its capitol building is actually rather unique (unlike say... Montana and SD, who seemed to somehow have hired the same architect with the same set of plans. I'm all for 2 for 1 deals, but come on guys... this is a capitol building, not a pair of shoes!).
Minnesota - Ahh... the state of 10,000 lakes. Thats 10,000 more places for mosquitoes to breed... Damn those things. I was eaten alive in a rather foolhardy attempt to camp one night, and will forever curse any place that combines hot humid temperatures with large standing bodies of water. That aside, Minneapolis-St Paul is quite the bustling metropolis. It strangely reminds me of Boston, with the river running through the center and a bunch of differing and small niche districts. Its got none of the scale of a large midwestern town like say Chicago or Indianapolis but it does manage to cram quite a bit into a rather small downtown area. The surrounding areas... well thats still up for debate at this point. It seems to be a hodge-podge of large commercial zones, as if a Sim City player decided to zone light commercial and accidentally made that the entire perimeter of the city.