I agree with the first two responses. The pendulum swings back and forth, and we do not want something as fundamental as the Constitution to swing with with it. One example not all that long ago was a proposal to add an amendment to allow foreign-born citizens to be eligible to be president. This movement was the result of discussion about Arnold Schwarznegger as a possible president, so such an amendment would have removed that obstacle from his candidacy. Of course, subsequently, his behavior removed him as an otherwise viable candidate, so the discussion of an amendment ceased. We really don't want amendments to be the result of such personal agendas, do we? The framers knew exactly what they were doing in making it so difficult.
It is relatively difficult to amend the US Constitution, but I think that is a good thing. If the Constitution was easier to amend, we would constantly be getting fickle changes like the sate referendums. These changes would represent passing trends and not true needs.
For me, they're just about right. You would not want to have the procedures be any easier to complete. We would not, for example, want to be able to push a constitutional amendment through if only 26 or even 30 of the states wanted it. You don't want to have parts of your fundamental law that half your country disagrees with.