Why shoud I use GlassFish V2 instead of GlassFish V1?

Adding to the great development features available in GlassFish V1, GlassFish V2 adds enterprise features such as:

• Clusters (screencast)
  • Scalability: Dynamically grow or shrink the size of a cluster to meet demand
  • Availability: Using in-memory replication, user sessions are replicated to more than one node. If an instance fails then session data is recovered from another node without service interruption.
  • Single point of management: Clusters can be managed as a single entity, offering a single point of deployment and configuration.
  • Setting up a cluster is extremely easy to do. In fact, the developer profile can be upgraded to a cluster profile with the click of a button. (screencast)
• Performance: GlassFish V2 delivers record-breaking performance.
• Advanced administration and monitoring
  • Clusters are managed from a single location. Clusters can be created, configured and "populated" with application server instances dynamically all from a centralized administration console.
  • Applications and containers can be monitored from a single location
  • Call-flow analysis tracks a transaction as it moves through the application and various application server containers while capturing time spent in each, facilitating problem resolution.
• A web server load balancer plugin is available for the Sun Java System Web Server, IIS and Apache. The plugin supports weighted and round-robin algorithms.
• Project Metro - a high-performance, extensible, easy-to-use web service stack. It is a one-stop shop for all your web service needs, from the simplest hello world web service to reliable, secured, and transacted web service that involves .NET services.