The New Republic makes some very good points on the matter:
The moderates have done something else typically maddening. They have redefined the center of debate to the rightward position demanded by the pull of Republican extremists. Back in the Clinton years, the idea that a president could shove judges down Congress’s throat was a foreign one. Republicans clearly thought so, because they used all manner of blocking tactics (albeit less visible ones than the filibuster) to stop dozens of Clinton nominees. Sure, Democrats howled in protest. But they never resorted to changing Senate rules.
In the Bush era, by contrast, Republicans have gradually removed various means of blocking judges and mounted a fierce assault on the filibuster. The filibuster still holds, for the moment. But allowing the confirmation of three radical Bush nominees—Priscilla Owen, Janice Rogers Brown, and William Pryor—in exchange for a Democratic promise to filibuster only in “extraordinary circumstances” created a false equivalence between the extremity of the GOP’s approach and the Democrats’ simple adherence to Senate rules.
Moreover, when the filibuster fight comes to a head again—as it will—the Democrats’ task will be made all the more difficult not only by the need to demonstrate “extraordinary circumstances,” but by the implication that the three Bush nominees the deal effectively confirmed, whom the liberal establishment treated as something close to worst-case picks, did not constitute “extraordinary circumstances.” That sets the bar awfully high. (Even some conservatives have fretted over Brown’s onetime suggestion that she observes a higher law than the Constitution.) Furthermore, what happens should Bush choose one of these three to fill the next Supreme Court vacancy? The answers to these questions all seem to favor the Republicans.