When leaving Laos, at least at the Lao Bao border, you will be surrounded by dozens of aggressive money-changers shouting in your face to change your Lao Kip into Vietnamese Dong. We didn't like the pressure so we refused to do this; we had a few Dong already; we thought we would change the Kip later.
Unique Suggestions: No matter how aggressive the money-changers are or how bad their exchange rates, get rid of the Lao Kip then and there. We were never able to convert these over in Vietnam, Malysia, or North America. We never got rid of them.