I've been an organ donor for three years and during these years I've met so many people whi disapproved of it for reasons like "It's just ... eeerr... I don't know ... it's disgusting" or something.
But what does anyone need his body for after it's dead? It doesn't hurt you if they cut you open and take your heart out after your dead. It will help another person to live! Just imagine you would be in a car accident tomorrow and you'd need a new heart or kidney in the next three days or you'll die. And no one is willing to donate one ... and you will die because other people thought that they want their body to be perfect while rotting underneath the earth.
In fact there is no reason why you shouldn't be an organ donor... just so many why you should.