MBSA 2.0 is the next version of the Microsoft Baseline Security Analyzer, which utilizes the Windows Update Services infrastructure for security update scanning. You can sign up for the beta of MBSA by nominating yourself through visiting http://beta.microsoft.com, sign in to the system using your Passport ID and a guest ID of "MBSA20" and completing the survey.
You can also find out more about MBSA 2.0 from Mike Chan, a Technical Product Manager through his webcast "Microsoft Baseline Security Analyzer 2.0: Architecture and Scenarios" which is a level 300 talk on Thursday 26th May between 11AM and 12:30PM PST (ie a 7PM start for us "Brits" which unfortunately, I think, makes it clash with Eastenders [;)])
Here's Mike's description of the session and the link to register.
Microsoft Baseline Security Analyzer (MBSA) 2.0 provides many new and powerful features, including integration with the new Windows Server Update Services (WSUS) infrastructure. Come learn about these new features and architectural changes to help make your IT infrastructure more organized and unified. Knowing what a complex process patch management can be, this session shows how to use MBSA 2.0 in common scenarios to improve your security update management process.