New features in the Beta of Microsoft Security Essentials include:
Enhanced protection through automatic malware remediation - The Beta will clean high-impact malware infections automatically, with no required user interaction.
Enhanced performance - The Beta includes many performance improvements to make sure your PC performance isn’t negatively impacted.
Simplified UI - Simplified UI makes Microsoft Security Essentials Beta easier to use.
New and improved protection engine - The updated engine offers enhanced detection and cleanup capabilities.