This hand-wringing from Bernie camps over consistency and "flip flopping" is some disingenuous gatekeeping bullshit. It's great that Bernie has been a champion for his ideals for fifty years, but to accuse Warren of just going with the current is preposterous. Yes, she was a Republican for a long time, but that was over true conservative economic policy. When she saw the realities of consumer bankruptcy and finance, she took in this new information and moved to the Democratic party. She's been a card-carrying Dem for over twenty years since. This kind of intellectual evolution is what you want in a presidential candidate -- it proves she can surround herself with experts, listen to the experiences of real Americans, and make the best choice based on the data. This history and evolution will be a real boon to her in the general, as she has first-hand experience that will help her wake up middle class Americans that vote against their interests by voting Republican. She learned to see beyond the lies and posturing by the GOP and promptly broke with them.
The move to not accept big money in the general is along the lines of responding to criticism and adjusting as necessary. The entire democractic process is based on picking a candidate that you feel will listen to your concerns and act accordingly, not just blindly follow their own will. Folks were worried she would be susceptible to lobbying and bribes, even though that's totally against her anti-corruption platform. So rather than insist she's above that, she decided to put her money where her mouth is and forego the donations.
Bernie may have a long history of leftism, but look at policies where he has been under legitimate criticism, like his stance on the fillibuster. He hasn't made a damn change in response to seeing how it is actually utilized in modern politics -- he's clinging to it as a theoretical concept. I'd much prefer a candidate who is able to respond to new information and who can fairly assess every side of an issue and come up with the best possible solution.