Hillary is actually quite close to me ideologically, just I don't entirely trust her judgment on a number of issues, and she's a pragmatist which is in some ways a good thing and in some ways means you can't really tell what she'd be like in office. (TO BE CLEAR presidents who barge forward according to what their ideology says to do regardless of circumstances... well, we remember Mr. Bush, right?). That said, I'm still to the right of Bernie, so. The biggest worry is, weirdly enough for a Secretary of State, foreign policy; I think that "doveish POTUS, hawkish Sec State" is the right balance to strike. "Hawkish POTUS, hawkish Sec State" risks groupthink, so I'd definitely hope that Hilary doesn't screw up there and get the advice she wants to hear, not the advice she needs to hear.
http://www.vox.com/2016/4/25/11505126/poll-hillary-clinton-donald-trump
http://www.vox.com/2016/4/22/11472026/2016-democratic-primary-party-unity
Basically all the 'ugh Hillary is not pure' crap will disappear when it is her against the Republican party.
This is a bit risky, though, because in first-past-the-post, even losing 2% of your voters to a splinter candidate is dangerous, as is another 2% of your voters being disaffected and staying home. It's oftentimes very hard to poll such people, especially the disaffected ones - polling any small subset accurately is tough.
I think 2000 both taught some of the far left a lesson, and also provided something for all leftists to rally around: hating on Bush. So there was a large degree of unity on the left for 2004 - 2008, and by and large, the left was pretty happy with Obama in 2012 - some of the left was disappointed, perhaps, but not in revolt. 2016 is uncharted territory. The good news for the Dems is that Trump or Cruz would both represent unusually soft competition where the difference between a 10-point rout and an 8-point rout is not decisive. But if something weird happens to make the race tighter, or we're talking 2020 when memories of Nader 2000 have faded further... who knows.