While testing the chat-portlet example, I noticed that chat would work only intermittently. The problem looks to be related to how the ViewState element of certain forms is applied/updated/removed. Further testing reveals that it's not specific to portlets. The chat sample that the chat-portlet is based on shows the same issue.

To replicate:

1) Build and deploy the core/chat app to Tomcat
2) Open 1 browser instance (e.g. Firefox) and navigate to the chat application (e.g. http://localhost:8080/chat/ )
3) Enter a handle and login to the chat
4) Open a second browser instance (e.g. Chrome) and navigate to the chat application
5) Enter a handle and login to the chat. At this point, the chat log should show in both browsers that the 2nd user has joined the chat.
6) Return to the first browser, enter a chat message, and click send. The message never gets sent and the chat log does not show any updates.