Having read being and nothingness, I can say that sartre was clearly a gifted narrative writer- and the literary criticism view of Hegel's phenomenology as the story of the movement of spirit might aptly be applied to Being. His notion, and I say notion with a capital N and all of the neo-hegelian implications (that is to say marxist implications), of Bad Faith I think shows that he had not enough care for Hegels original intent...
Furthermore it is clear that heidegger had nothing but contempt for sartre, and probably avoided the title 'existentialist' for this very reason.
So one must begin any critique of Sartre by addressing how, as Robert Solomon said, sartre places a critical emphasis on autonomy and free will. He says essentially, the choices you and I make determine what kind of people we are and we need to be responsible in an existential sense towards authenticity in action.
So immediately, we get the sense that sartre has departed from phenomenology as such- and has taken up the torch of a kind of Husserlian turn on Heidegger's worldview- without the phenomenological components of sartres contemporary Merleau Ponty nor the poetry of Camus.
And of course, a critique of Sarte has to address No Exit. This is basics, but what is Sartre really trying to say in No Exit (a book that is cursory reading in highschools across america)?
He is basically laying down the foundations of new age 'free will' thinking for ages to come!
All for an in vogue husserlian who lived in nazi germany during frances occupation!
I think in our modern age of philosophy, and nietzsches new philosophers arizing on the heideggarian horizon- I think we can all put a little holderlin to the test-
"Go Down then lovely sun for but little they
regarded you, nor holy one, knew your worth,
since without toil you rose, and quiet,
over a people for ever toiling.
to me, however, kindly you rise and set,
o glorious light, and brightly my eyes respond,
for godly, silent reverence I
learned when diotima soothed my frenzy
oh how i listened, heavens own messenger,
to you my teacher, lover, how to the golden day
these eyes transfused with thanks looked up from
gazing at you. and at once more living
the brooks began to murmer, more lovingly
the blossoms of dark earth breathed their scent at me
and through the silver clouds a smiling
aether bowed down to bestow his blessing"