The Cowgirl Museum showcased women of no-nonsense character, pioneer (and pioneering) achievement, physical daring, and unapologetic femininity. Full of inspiring role models, the museum presented a piece of feminist history that gets left out of the city-oriented accounts most of us learn...
I think this both smart and, more usefully, right. Palin represents a certain ideal of American womanhood. It is easy to joke about moose-hunting and all the rest of it, but she taps into an ancient American tradition. To put it another way, she wouldn't have the same impact if she came from Alabama or Ohio. Her westernness, the sense of the frontier, pioneering spirit is a significant, telling, part of her appeal.
On the one hand, she represents the pioneering spirit that built the United States in the first place; on the other there's an element in which, culturally anyway, she represents the common sense integrity of the frontier in contrast to the intrigue and squalor of viperous Washington. That helps explain, I think, why there are plenty of people who won't be too concerned by the reality of her record in Alaska (whatever that may be). A reforming governor taking on corruption is a vastly more powerful story of it's taking place in the west than it would be if it were a governor in, say, New Jersey or Georgia. The idea of the west trumps all other considerations. As the old newspaperman put it, "This is the west sir, when the legend becomes fact, print the legend".
That's also, I think, why it isn't an immediate problem that Palin's speech was, as Ross says, in many ways an orthodox, old-time conservative speech. The style mattered more than the substance. Or rather, the substance was the style. Similarly, it wasn't terribly significant that Obama's speech in Denver was, in policy terms, little more than a laundry list of traditional liberal concerns that could have been given at any point in the past 25 years. Again, it was the style that mattered.
In Palin's case, of course, none of this offers any guarantee that she'd be a competent Vice-President, but it helps explain why she's a powerful candidate. She's the cowgirl-turned-Sheriff whose presence on the ticket taps into one of the oldest, most potent American stories - or, if oyu prefer, myths - of them all.