I knew his choice was not going to be one of the names the mainstream media kept bandying about right up to the announcement. A while back I had heard her name mentioned in only semi-serious passing and, since I knew literally nothing about her, read up on her a bit. I decided then that she was my preferred choice. She complements a lot of McCain's perceived shortcomings in that she is a she, she is young, and she is conservative. That she's a woman is ultimately irrelevant, but it can only be a plus. Those who think McCain should have chosen a more "moderate" running mate, like Lieberman, fail to see the reality of his situation. His credentials among the conservative wing of the party are scarcely better than Hillary Clinton's; if he is to have any chance of winning the election he has no choice but to energize that conservative core of the party. A dull, uninspired choice in running mate would only increase the likelihood of disaffected conservatives not voting at all.
I can say that her selection has made me more interested in voting for their ticket, rather than simply voting against the other one. There are things about her I do not agree with, such as her view that creationism is a valid subject in science classrooms, but frankly I am at a point where I am willing to accept the candidate who is imperfect in that they are more conservative than me, rather than again accepting one who is imperfect in that their "move to the middle" means they're going to play no more than lip service to their supporters' core beliefs.
She brings something else to the ticket that is appealing, I think. She is someone who went into politics almost because she felt like she had to, rather than spending an entire life scheming and polishing herself for a whole career in public office. I don't think I am alone in finding that refreshing. The whole question as to whether or not she is qualified is almost laughable considering who the other ticket is pushing as their top guy. I think 2 years as a state governor is at least equal to a few years of voting "Present" in the Senate.
To summarize my view, this is the first time I've really felt a desire to vote FOR anyone. I don't know if that's just because she is somewhat a novelty right now, but I think there's more to her than that.