Which aspect of the ending, the ending of the novel itself or the "historical notes" appendix?
I thought the ending of the novel itself was fine, it's certainly not the only novel or story to end on such an ambiguous note. But the appendix fudged the issue a bit - while it was amusing to read, it seemed to be almost as if Atwood was saying "But really it's okay, I got a bit dark in this novel but it all ends happily eventually." Which weakened the impact of the novel for me, somewhat.