On what sort of note does the story end?

It is a happy ending that has undercurrents of sadness. Gregor dies in his room. The family is now free of the specter of Gregor. His presence was a perpetual reminder of alienation. Without him, they are free to once again to continue living, believing that life is good and the future is bright. The family suddenly feels whole again. Still the fact that they forsook their family member always remains upsetting.