I actually don't find it terribly surprising that liberals haven't shown any outrage over Barack Obama's dinner party with George Will, Charles Krauthammer, Bill Kristol, and David Brooks. I'll get to my hypothesis why liberals aren't upset in a moment. But first imagine this counterfactual: George W. Bush (or maybe a victorious John McCain) sat down before his first inauguration with Paul Krugman, E.J. Dionne, and Frank Foer. Would conservatives have reacted with the same equanimity? No, I think they'd have gone nuts. And the reason is that they wouldn't have confidence in Bush or McCain to be surrounded by liberal ideas without being deeply influenced by them. I don't think they'd have reacted this way if, say, a President Mitt Romney did the same thing.
And that's why liberals aren't having a cow. They know that Obama understands far more about policy than any of his right-wing dinner companions, is used to being exposed to opposing ideas, and won't come out of that dinner telling his staff, "Hey, did you know we cut half the capital gains tax and raise more revenue?"
A separate issue is why Obama didn't pick some conservatives with a bit more intellectual integrity than, say, Kristol and Krauthammer. The problem, of course, is conservatives like that tend not to rise to positions of high influence.