bin/twiddle.sh doe not work in AS5.0 because of missing security classes.
A scan on client jars shows that SecurityContextAssociation is not part of any client jar

[tdiesler@jbws jboss-5.0.0.Beta3]$ bin/twiddle.sh -s jnp://jbws2:1099 get jboss.system:type=Server Started
Exception in thread "main" java.lang.NoClassDefFoundError: org/jboss/security/plugins/SecurityContextAssociation
at org.jboss.proxy.SecurityActions$1.getPrincipal(SecurityActions.java:57)
at org.jboss.proxy.SecurityInterceptor.invoke(SecurityInterceptor.java:58)
at org.jboss.proxy.ClientMethodInterceptor.invoke(ClientMethodInterceptor.java:74)
at org.jboss.proxy.ClientContainer.invoke(ClientContainer.java:101)
at $Proxy0.getAttributes(Unknown Source)
at org.jboss.console.twiddle.command.GetCommand.execute(GetCommand.java:168)
at org.jboss.console.twiddle.Twiddle.main(Twiddle.java:305)