You definitely want to go.

Luxor is one of my favorite places in Egypt and is the largest open air museum in the world. Others have mentioned many beautiful temples so I won't repeat those. I'll just add a couple more.
Medinat Habu is one of my favorite temples. It is one of the most colorful and least crowded.
Dendera Temple can be done as a day trip (you have to join a convoy) but it is absolutely stunning. You can also do it via the Lotus Boat where you spend a full day sailing on the Nile (there and back). It's a long day but very relaxing.
Aswan and the Nubian people are near and dear to my heart so do consider visiting there as well if you go.

You can visit
Philae Temple and
Abu Simbel (3hrs by road from Aswan) has to be seen to be believed.
EDITED TO ADD: All convoys, with the exception of Aswan to Abu Simbel, have been discontinued. Tourists are now free to travel at their own convenience. :-)