Exit polls tell a different story regarding Palin. She may not be your cup of tea, but the numbers say she helped.
I suppose it depends on which exit polls you look at. Something like 15% of voters switched from McCain to Obama, and Palin was cited as the #1 reason for switching. I think Palin was disastrous for him. Gave him an immediate bump, but that disapated in a few weeks and, ever since then, she's been a liability.
There was an exit poll question about Gov. Palin given to both Obama supporters and McCain supporters. More McCain supporters felt she was an asset than Obama voters felt she was a detriment by 11 percentage points. Her nomination was wrongly reported as a move to get Clinton voters; it was to shore up the Base. She brought them out when they would have stayed home. In the end it still wasn't enough, but she actually helped McCain.
I'm not sure that proves much. How Obama voters felt about Palin isn't all that relevant, IMO. I don't judge her based on her ability to "steal Hillary supporters." I think the fact that she eroded as much as 15% of McCain's previous support is quite disastrous. To me, that says a lot more than the fact that she was more favourable to eventual McCain voters than disfavourable to eventual Obama voters.
I think McCain's eroded support is largely due to the economy. Under socialism, the masses will be taken care of through redistribution of wealth.