Daily Kos has a good discussion of the issue over the filibuster and judicial appointments. I was going to write something up about that myself, but as with so many blog ideas, I never quite made it.
My eye was caught the other day by Juan quoting Federalist Papers #10, where Madison warns about the potential for the tyranny of the majority in a democratic system. I have the clearest memory of reading a handout of this back in my college days, in an Economics class, and the professor saying to us "You think we live in a democracy, but we don't". Actually, my memory is that this particular teacher rather disapproved of the sentiment. But I remember Madison talking about the possibility of a "factious majority", and being rather stunned that a majority of the people could be considered a "faction".
It's real simple: If the judiciary is to be independent, and not just an extension of the executive branch where a president can simply pack it with judges congenial to his ideological outlook, then the Senate must be allowed to function as a check on that, not just as a rubber stamp on whatever the President wants.