A risky choice. On the one hand, you can't connect her in any way with Bush or Washington. She's truly a political outsider in that respect. The downsides though potentially outweigh the upsides...
1) She has limited political experience. As the VP is only a heartbeat away from the presidency, her nomination undermines the McCain position that Obama is too inexperienced to become president. If Obama is too inexperienced, what does that make Palin?
2) Gender is not a strong predictor of vote choice. If this was meant to woo female voters, or Clinton-leaning voters in particular, it will probably fail. The strongest predictors of vote choice remain partisan affiliation and strength of partisanship. Bush and Kerry split the female vote almost 50-50 in 2004, which is unsurprising since that's pretty much how the parties split in the electorate. It would be surprising, though I suppose not impossible, if gender were to suddenly become an important factor in this election.
-- Todd/Leviathn