It always pays to leave well
When someone leaves a company there are two sides to it.
The first side is the way the employee behaves and handles themselves. I always aim to be professional and work hard until the moment I leave the office for the last time. I like to think that is one of the reasons my last four roles have involved word of mouth recommendations.
I have seen some people, who were excellent up to that point, almost switch off once they have announced they are leaving. These are people that I would have, up until that point, considered recommending in future but this single act of unprofessionalism at the end tainted my overall view of them. One ex-employee took it to an extreme and spent the whole of his last month just reading Dilbert cartoons!
The second side is the way the company treats the employee who is leaving. The article below, to me, shows the way this should be done. It emphasizes that they care for their employees as people. I can't do it justice here so just read the article.