Terry Eagleton writes here about Rousseau. It seems a good, short summary:
Above all, Rousseau is the explorer of that dark continent, the modern self. It is no surprise that he wrote one of the most magnificent autobiographies of all time, his Confessions. Personal experience starts to take on a significance it never had for Plato or Descartes. What matters now is less objective truth than truth-to-self – a passionate conviction that one's identity is uniquely precious, and that expressing it as freely and richly as possible is a sacred duty. In this belief, Rousseau is a forerunner not only of the Romantics, but of the liberals, existentialists and spiritual individualists of modern times.I liked this line too:
It is true that he seems to have held the view that no identity was more uniquely precious than his own. For all his cult of tenderness and affection, Rousseau was not the kind of man with whom one would share one's picnic. He was the worst kind of hypochondriac – one who really is always ill – and that most dangerous of paranoiacs – one who really is persecuted. Even so, at the heart of an 18th-century Enlightenment devoted to reason and civilisation, this maverick intellectual spoke up for sentiment and nature. He was not, to be sure, as besotted by the notion of the noble savage as some have considered. But he was certainly a scourge of the idea of civilisation, which struck him for the most part as exploitative and corrupt.
Rousseau ranks among the great educational theorists of the modern era, even if he was the last man to put in charge of a classroom.