In today's Washington Post James Mann's "Understanding Gates" questions how much of a change Gates will be over Rumsfeld. Mann's caution that we cannot be certain precisely which position Gates will take on Iraq is well taken. Nonetheless, I strongly disagree with Mann on one point: "Rumsfeld was never a neoconservative; he was an obstreperous contrarian, committed not to putting forward any particular philosophy but to aggressively challenging whatever ideas his bureaucratic opponents and critics put forward."
Rumsfeld, as I think a reading of Mann's Rise of the Vulcans shows, was not simply a "contrarian". He was, except for very early in his career, a consistent advocate of 1) suspicion toward and confrontation with the Soviet Union, 2) over-estimates of Soviet military power ("Team B"), and 3) virtually unlimited increases in defense spending to "protect" us from the Soviets; finally, 4) he was the man who strongly advocated and had virtually sole responsibility for executing the Iraq War. Rumsfeld may not have been a "neo-conservative" in precisely the same sense that Paul Wolfowitz, Richard Perle, and Douglas Feith are, but who hired all three of them for top jobs in his Defense Department? I'm willing to grant that Rumsfeld is not as consistently considered a "card carrying" neo-con but there is precious little light between his positions and those of the usual neo-con suspects; and referring to him as simply a "contrarian" is one of Mann's characteristically overly charitable accounts of the "Vulcans".
Mann's points about Gates' history are definitely worth taking into consideration and only watching Gates' performance and who he allies with will tell us where he stands today on Iraq. Reading the Wikipedia article on Gates suggests additional reasons to worry about how much of a pseudo-conservative he may turn out to be.