It is really a toss up most of the time. It can be actually very stressfull being a GP (Grandparent). We find ourselves worrying alot more about our GK (Grandkids) than we did our own children oddly enough and I believe that is because we have lost a certain element of control over things.
But in reference to your question, When they put thier little arms around you and squeeze tight. The smile when they see you and cry when they go home...
The best past of being a GP for me is knowing that they will listen to me alot more than they ever will thier own parents! Ha Ha..We give them a safe place where they can be themselves and they allow us to be silly and childish with them.
They are really such a blessing!