I broke down and finally watched Frozen a few months ago, after the Once storyline was announced. Thought it was actually pretty good... although I'm having trouble understanding why it's become the mammoth hit it's become, since the story doesn't seem all that original or groundbreaking.
Unless it all really does just come down to kids loving the funny little snowman character.
It's groundbreaking by comparison to almost every other Disney film ever made. The prince is not the hero, the villainess is not actually a villain and the act of true love doesn't involve the prince and the princess riding off in a chariot. I don't know what would have to be in it for you to consider it "groundbreaking", but what i saw was enough or me.