WHAT is there about Mikhail S. Gorbachev that has made him an instant favorite of the American media? Has he proceeded with new meaningful initiatives, opening the door for rapprochement with the United States? Has he begun dismantling some of the most petty Soviet domestic-control mechanisms? Or has he managed, with a broad smile, firm handshake, and quick wit, to mesmerize quite a few commentators without yielding an iota of his neo-Stalinst regime's practices? ``The obsession with style over substance among some observers is ludicrous,'' writes Richard Nixon in the most recent issue of Foreign Affairs. Indeed, the new Soviet leader has made major headway in the public relations battle with President Ronald Reagan, almost exclusively because he proved to be good copy. But Gorbachev's words and deeds should be assessed not on the basis of his performing talent, but through the prism of US interests and values. If this prism is used, the enthusiasm over the gene ral secretary's conduct appears to be premature.
His arms control pronouncements are more in the mode of outmaneuvering the Reagan administration in the propaganda war than seriously negotiating with it. Gorbachev was told in advance by Washington that his nuclear testing moratorium was a nonstarter. But he announced it anyway to score a point. The Soviet leader was well aware that the United States was opposed to an international conference devoted to outlawing the Strategic Defense Initiative (SDI). That did not deter Moscow from calling for precise ly such an event.