I didn’t know we had a resident legal expert. I too am looking forward to hearing what he or she has to say. However, since I went to law school, I figured I’d chime in on this topic in the meantime.
First and foremost, I frequently have an internal debate with myself over the normative question of whether we should still care about the Constitution. It is true that the people who framed the Constitution were innovative, smart men. I also think that the Constitution remains indispensible in dictating the structure and function of the various parts of our government and in preserving the separation of powers.
But I often ask myself why we look to the Constitution to see if, say, abortion should be legal. I think it’s very correct of you, CH, to say that there is a cumbersomely voluminous body of law surrounding the Constitution, to the point where many of the doctrinal underpinnings of modern constitutional law seem almost silly. You mentioned a good example of this: the “right to privacy” that has been read into the Fourteenth Amendment. Although I am quite pro-choice, I am unhappy that the legality of abortion in this country rests on those shaky grounds. Why can’t we base our jurisprudence on more contemporary considerations?
It also bears mentioning that the reason you haven’t heard any grumblings over federal involvement in education is because of the very expansive reading of the Commerce Clause. (By the way, there are people -- collectively known as "crazies" -- who argue that the federal government should not be involved in education and various other activities.) Today, the Commerce Clause is the basis for the vast majority of federal legislation, and up until a few years ago it was seen as virtually limitless in its reach (the Supreme Court has recently reined it in a bit). For that reason, the Tenth Amendment (and the Ninth Amendment, for that matter) is a lot less powerful than you suggest it should be.
There is, however, one upside to having such a complex body of law surrounding our Constitution: it generates quite a lot of business for lawyers. :-)