The reader knows that Kundera rejects Nietzsche's myth from the very beginning. This being said, I believe Kundera is somewhat of a hypocrite. Kundera uses the characters to explore the different paths he could have or might have taken as well as the different possibilities he could have realized- it is an experiment of some sorts. There are several instances of repetition throughout the novel; for example, Part 1 and Part 2 basically tell the same story but from a different narrative perspective.The same patterns such as these are recurring, forcing the idea and presence of eternal recurrence upon us. Like Ms. King said, Kundera has the advantage of recreating different possibilities with these characters through the repetition of their stories. Therefore, if Kundera really disagreed with Nietzsche so much, why would he constantly write about such repeated stories and patterns? If things in our lives really happened only one time as Kundera wants the reader to believe, wouldn't he have just written the story only one time?
I might be totally missing the point here, but that's my two cents on the matter.