When we bought our house, we knew that replacing the doors was something we'd need to take care of pretty soon. The windows were all new and energy efficient, but the doors...not so much. So we finally bit the bullet and purchased a new front door, patio doors, and the door that goes into our garage. we're really happy with how everything turned out.
Before (inside of the front door):
Before (patio doors/playroom-see the nice scratches from the dogs that lived here before?):