From the http://blogs.technet.com/kevin_beares/archive/2007/11/07/windows-server-centro-is-officially-unveiled-and-has-a-new-name.aspx a small amount about Centro and the tech beta.  This is produced by the same team who build SBS 2003 R2 and SBS Cougar. More on those next year.

Windows® Essential Business Server is the new Microsoft server solution for small to medium businesses, with 50 to 250 client computers in their organizations. Windows®Essential Business Server offers a standardized server configuration that is designed to meet the needs of most midsize businesses. The configuration is optimized to meet the currently recommended practices for networking, security, collaboration, and remote access. The tightly integrated Windows Essential Business Server simplifies setup, migration, and licensing for Microsoft infrastructure server products that a midsize business uses most frequently. Most network services and resources are managed through a single Windows®Essential Business Server Administration Console, which is accessible from anywhere on the network or remotely over a virtual private network.

Windows®Essential Business Server is installed on three physical servers. These are referred to by their primary roles in the network:

• Windows®Essential Business Server Management Server – Centralizes management of your Windows Server "Centro" network. Enables and manages worker collaboration and network services.
• Windows®Essential Business Server Security Server – Manages security, Internet access, and remote-worker connectivity.
• Windows®Essential Business Server Messaging Server – Provides messaging capabilities and manages network services.

If you are interested in joining the Windows®Essential Business Server upcoming Beta 2 effort;

1. Please go to http://connect.microsoft.com,

2. Click on Invitations and sign in with your Windows Live ID (Passport ID).

3. Enter the following invite ID: EBSE-VKDP-276Y. 

4. You will be asked to take a short survey.  

5. Once you complete the survey we will evaluate your application for participation in the Techbeta.

6. Then look for an email from [email protected] with further details.

ttfn

David