For the record, I have not read the Batman comics that much so I didn't know she was supposed to die, and I liked Katie Holmes as Rachel Dawes far better than Maggie Gyllenhaal. Seriously, Maggie Gyllenhaal looks too old in The Dark Knight to be the same Rachel from Batman Begins. There are a number of shots in TDK where I could swear she appears to have greying hair, and her facial complexion makes her look older. I know this could be fixed with makeup, but it wasn't.
Also, Maggie Gyllenhaal's voice cracks on occasion during her lines in TDK.