We don't have one out of the box, but the Developer Division Aftermarket Solutions team is considering creating such a tool. Currently you have to manually update users in 3 places, which is far from ideal.

If you're interested in such a tool, please visit their blog and leave a comment.

I wish we had had the bandwidth to do something ourselves but this is one of those hard cuts that we've had to make in order to ensure that all our resources are focused on getting a high quality core product out of the door as rapidly as possible without introducing any new risks.