Regarding performance, Glassfish v2 is 70% faster than the previous release, as Sun's Scott Oak reported in July. Scott attributed the improved performance to "... substantial performance improvements across the board: in the servlet connector and container, in JSP processing, in the local EJB container, in connection pooling, in CMP 2.1, and so on. "
Glassfish v2 also includes better Java/.NET interoperability via Web Services Interop Technology (WSIT). At this year's JavaOne, Arun Gupta demonstrated secure Glassfish/.Net interop using WSIT. In his video, Arun shows an Excel 2007 spreadsheet running in Vista with live links to data securely managed by a WSIT endpoint on a GlassFish app server.
Most of Glassfish v2 is released under both Sun's Common Development and Distribution License (CDDL) and the GNU General Public License (GPL v2). A few components, including JavaServer Faces Templating, are only available under the CDDL.
Sun has also updated its commercial version, Sun Java System Application Server (SJS AS) 9.1, which includes paid support, natch. Eduardo Pelegri, Distinguished Engineer at Sun, describes the relationship between Glassfish v2 and SJS AS 9.1, and the process for keeping the two in sync in Productizing Open Source Projects - The GlassFish Approach. For more info, visit the SJS AS 9.1 main page.
The Glassfish Project also has a technology preview of the upcoming Glassfish v3 available for download. Version 3 will feature a more modular architecture allowing users to invoke individual components as needed.