Windows Defender Beta 2

Paul Thurrott reviews Windows Defender (formerly Microsoft Antispyware, formerly Giant Antispyware), and its well worth the read.
Thurrott reports that the reason for the long delay is Microsoft needed to rebuild it from the ground up in order to prepare for a 64 bit future, and to allow for region language versions amongst other reasons.
I haven’t tried it out for myself yet, my computers are busy troubleshooting a work problem. But their is some cool stuff here such as it pdates through the automatic updates service.
One thing I am wondering is, will this download automatically through the update mechanism of beta one? All I have heard is that I can install beta 2 over beta 1.