A couple of the Powerline guys got this well-written, simply stated article published in the Washington Post, explaining why it is good thing that Harriet Miers is out and Samuel Alito is in. One thing they point out is this: "The Republican talent pool is deep and broad, in a way that it was not when Presidents Richard Nixon and Ronald Reagan were appointing judges." I certainly agree with that.
They claim that the reason why court nominations have become more contentious is that liberals rely on the courts to overcome the unpopularity of liberal ideas: "Liberals increasingly came to view the court as a legislature of last resort, where policies too liberal and too unpopular to be enacted by real legislatures could be mandated by fiat of the court's liberal majority."
They describe what they claim conservatives want in judges: "We want judges who won't make stuff up," to which they add the corollary, that "judges also don't have the discretion to ignore language that is in the Constitution or the laws," including limitations on the powers of Congress.
They conclude: "The Miers-Alito moment shows that conservatives prefer demonstrated excellence to its absence, openness to stealth, and adherence to constitutional text to the promise of any particular result."
I recommend this article, whether you agree with it or not, as it is well-written.