The only real liability Hillary has is that she would be a Clinton following a Bush following a Clinton following a Bush. Her election at a minimum would represent 24 straight years where the president was from one of two political families. A tad monarchial. That said, I think she has to be considered the prohibitve favorite. Every time I see her on TV she comes off as smoother and more polished (without comprimising on her authenticity). I think she is going to beat whomever the republicans nominate like a drum.
Oh yeah, she has one other liability, arguably her greatest asset as well... Billy Boy. God knows how much action he has been getting. But you know what, I don't think people care.