Did the Malfoys change in the end?
I don't think so, exactly.

I think their ordeal with Voldemort brought out a side of them that we would not have otherwise seen.

Narcissa, obviously. From the beginning of DH, she was a traitor to Voldemort, because he betrayed her and obviously intended to kill her son. And in the end, she lied that Harry was dead. Why she did this has been debated, but I don't believe that it was entirely self-serving. It would have been the right thing to do, whether or not her family would directly benefit from it. (Remember that she was not truly a Death Eater. She was connected by her husband and sister, but not in her own right.)

But even before that, back in OoP, I think Lucius himself showed some restraint. I think that his feelings were mixed even then, and that his heart wasn't really in it any more. Or that, had he fully realized just what he was getting into, he wouldn't have gone that way in the first place.

He would still be a prat. His values don't work for me. But I doubt that he was ever pure evil.