On the eve of the launch of OS X Lion, Apple has released a Migration Assistant update for Mac OS X Snow Leopard. The 714 KB update issues the following fix:
This update addresses an issue with the Migration Assistant application in Mac OS X Snow Leopard that prevents transfer of your personal data, settings, and compatible applications from a Mac running Mac OS X Snow Leopard to a new Mac running Mac OS X Lion.
In other words, this sounds like a critical update for anyone running Snow Leopard on their current Mac but planning on moving their data over to a new Mac with Lion as its OS.
Apple OS X Yosemite
Apple Mac OS X Snow Leopard