The following are two short screencasts demonstrating :
a/ the basic clustering infrastructure already available
b/ a new application versioning feature (external contribution)
Details for this clustering demo can be found here.
Check this document for more details about this versioning feature.
You’ll find more information about Milestone 1 and the future developments of 3.1 on the GlassFish Wiki.
The next milestone is currently scheduled for in about a month from now.