I think it is a strategic mistake, one of many the Republican election machine has made this cycle. Not that I don't like the person; from what I've read, she is quite honorable. But she is even less qualified than Obama.
4 years on the Wasilla (pop 5470) city council
6 years as mayor of Anchorage (pop 283,000)
1 1/2 years as governor of Alaska (pop 683,000)
This is essentially your local politician. Look at the people on your city council, or the mayor of your city, and imagine that person as president or vice-president. Imagine Scranton mayor Chris Dougherty as potential presidential material. An honorable man, certainly. But not a president.
So all of a sudden, the one thing that McCain could have hammered Obama on is no longer an issue; it is now the same for both tickets.
If you were already decided for McCain, then you'll like her. But if you are undecided, she isn't going to help him win. It doesn't make me (undecided) more likely to vote for him, it makes me less so. McCain goes down, and she's the Prez? I don't think I'd be real confident with that.
But yeah, she is really beautiful.