I just returned from 1-1/2 days in Cairo, and that was enough for me for that city. That will give you a chance to see the Light Show, the Great pyramids, sphinx, the step pyramids, carpet and papyrus schools the Museum and such. Unless you are interested in seeing garbage strewn streets, insane traffic, and irragation canals with floating dead animals, after the pyramids, Cairo isn't much. Get to Luxor or Sharm el shek or Answan.

If you are an egyptoligist, the above does not apply, of course.