BE CAREFULL WITH THIS UPGRADE !!
I've noticed on 2 different computers that after installing this upgrade, the migration assistant "version 1.2.4 (179.1 )" no longer works for transfering data from a Leopard (10.5) computer to a Snow Leopard (10.6) computer. Whereas with previous versions of the migration assistant it worked like a charm. I tested on the same computer, before and after installing this upgrade : before it worked, after it doesn't work anymore.
So, my advise is : only install this upgrade if you need to transfert your data to a Lion (10.7) computer. Otherwise, don't install it !!!