Should the Shuttle program be extended?

Over at Universe Today, Nancy Atkinson has written an interesting piece on whether NASA should consider extending the Shuttle program, which is currently planned to end in September of this year (or thereabouts, depending on delays). After that, NASA will rely heavily on private companies to ferry cargo to orbit, and eventually humans as well. My thoughts on this are already a matter of record: I don't think NASA should be in the business of doing anything routine, and several companies are gearing up to take over flights to low-Earth orbit (or LEO as it's called). SpaceX may be ready as early as late this year for unmanned trips to the space station. However, no private company has yet made a cargo launch capable of reaching ISS, and there may still be a gap in our ability to get into space. Extending the Shuttle program sounds like a good idea, ...