Furthermore, I was not able to get a clean TCK run against JBoss AS 6 M2
(with updated Weld) in my environment - I am getting 100+ failures
although nightly build seems OK in hudson.


Check the server.log. Out of memory? At one point you could fail because the jboss-interceptors version was old but if it's a clean M2 it shouldn't be a problem.
 
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Nik