Heidegger is a seducer. His central metaphysical intuition is very seductive. But, like most seducers, his 'ways' (his 'wiles') are utterly fraudulant. His use and abuse of etymology, his fetishizing of the ancient
Greek language, his very interpretations of the Presocratics, his 'teasing out' (accomodare) of meaning from ancient texts -- is all bullshit. He should have just written a poem or a prose-poem and been done with it....
As to his Nazism, it follows ultimately from his rejection of Plato and Aristotle, and the 'metaphysical-analytic' tradition by which he justifies his contempt for modernity.
(Of course, I know very little of Heidegger at first-hand -- so the above is nothing more than a set of impressions from secondary readings --)