There was a good article published by the AP that expresses my deepest concern about Hillary's candidacy - her high negatives.
AP has reported that a survey of Democratic insiders shows great concern with Hillary's possible drag on the rest of the ticket in certain states. They also noted that her high negatives (which tend to go higher as the campaign develops and the GOP attack machine gears up) are a real problem. You can read the whole article at http://news.yahoo.com/... There was a diary yesterday on this reporting that MSNBC had reported essentially the same thing.
This has always been my main concern about Hillary. While I think she has really done a good job in the debates and I was really impressed when I met her at the yearlykos break out session, there does seem to be a big chunk of the electorate that has already made up its mind about her in a negative way and most of those voters probably will never vote for her. For example, my brother-in-law, who is a loyal liberal Democrat, has expressed concerns about voting for Hillary. She is also the one candidate that could really revive moribund GOP turn out in 2008.