One common objection to Purgatory is that it somehow makes Christ's sacrifice on the cross unnecessary. I've never understood this. None of us could ever merit heaven without Christ. This is something that both Catholics and Protestants agree on.
As I have written before I like analogies. They help me to see complicated concepts more clearly.
Imagine that your child accidentally breaks your elderly neighbor's window. Your child is upset because he/she knows that he will have to have to admit his mistake to the neighbor. Yet being a responsible parent, you march your child nest door. The sweet elderly lady hugs your child and assures him that she completely forgives him. She isn't mad at all. But of course there is the detail of the broken window. Windows are expensive to replace. You promise to pay the charges but your child will have to work off the cost.
Is your child any less forgiven because he has to clean up his mess? Do you tell the elderly woman that her forgiveness doesn't count because your son has to do some work?
I don't want to get to heaven as I am, a person full of faults and sin. I welcome the chance to be made clean. How merciful and wonderful is our God.