The Clintons and John Edwards (and Paul Krugman and other pundits) pounced on Obama for these remarks, arguing that the liberal cause must repudiate, not praise, Ronald Reagan and the conservative movement whose champion he was. But Obama didn't say that conservative policies were effective or a good idea. He was making a different point, about the historical moment and the momentum of ideology and history. For better or for worse, the conservative movement has been, in fact, the most well-defined philosophically, and the most effective popularly, in American politics since the 1970s. This is in the nature of the pendulum swing of history, an inevitable reaction to the stagnation of the liberal approach to government that dated, by Jimmy Carter's time, all the way back to the FDR 30s (the political success of conservatism was not inevitable, but the movement was). So it wasn't entirely fair for Obama's opponents in the Democratic ranks to charge him with irresponsible burnishing of the Reagan myth (not entirely fair).
However I do have a problem with Obama's remarks, particularly as they were clearly meant to draw a contrast between himself and both Clintons. Obama was implying that unlike the Clintons, and like Reagan, he, Obama, is a potentially pivotal "agent of change." I must say I fail to see the parallel with Reagan here. Reagan was the spokesman for a systematic ideology that generated specific policy proposals. Barack Obama can claim no such mantle. I don't know of a single point of either ideology or policy where there is any essential distinction between Obama and the other Democratic candidates. He leads no movement, he offers no radical reapproach to the federal government. In fact, both Clinton and Edwards do a better job of laying out specifics.
What we really have here is a swipe at Bill Clinton. I can appreciate that Obama is feeling a bit angry and threatened from getting beat up on by the mighty Bill Clinton, larger-than-life popular former president. It is indeed an unprecedented spectacle, and I saw a report today that some Clinton friends and loyalists are warning Clinton to back off. But if Obama, in the privacy of his own thoughts, is telling himself that he, unlike Bill Clinton, is a pivotal, dialogue-changing figure like Reagan was, that's an error of judgement that does not reflect well on him.