Can you accept an apology that isn't heartfelt?

Rush Limbaugh recently made news by calling a woman who testified before the Senate regarding birth control, a “slut”.
He added: “So Miss Fluke and the rest of you feminazis, here’s the deal. If we are going to pay for your contraceptives and thus pay for you to have sex, we want something. We want you to post the videos online so we can all watch.”
Advertisers began pulling their products from the radio show, and Limbaugh issued this apology:
“My choice of words was not the best, and in the attempt to be humorous, I created a national stir. I sincerely apologize to Ms. Fluke for the insulting word choices.”
This apology was made on his website, not through a broadcast announcement.
Does this apology seem heartfelt?
Should this apology end the discussion?
Should Sandra Fluke accept this apology?
Should advertisers return to the radio show, or should they continue withdrawing, pending a better statement?
When someone offers you a half-assed apology, do you take what you can get, or do you wait for a better apology?