With Plug-in 2(Java 6u10), a whole new experience comes into Java Plug-in. I have mentioned the new features of Plugin2 in some of my presentations of 6u10.
For detail, please visit this link : http://java.sun.com/javase/6/webnotes/6u10/plugin2/index.html
Switching between old/new plugin:
Java Control Panel - Advanced - Java Plug-in - Enable the next gen plug-in.
(Check this link : http://www.java.com/en/download/help/new_plugin.xml)
By default, it will take new plugin, but untick it for old plugin.