New in this version:
Web Based Interface
Nessus 4.2 comes with a built-in web interface which lets you start your scan and analyze the results from any system which can connect to your Nessus scanner.
Enhanced Reporting
Nessus 4.2 lets you compare different scans. It also contains an improved report export format, with additional templates are being regularly distributed through the Nessus ProfessionalFeed.
Performance enhancements
Scans start quicker, plugins updates use less bandwidth, memory usage has been further reduced and the handling of network timeouts has been improved.
http://www.nessus.org/download/