According to Adrian's comment on JBAS-7465:
====
However, if the jms product already supports DLQ processing then you should disable
the DLQ processing in the MDB. i.e. useDLQ=false.

It is duplicate work and not as "reliable" as the jms product handling internally, e.g.
if the jms connection breaks between sending the message to the DLQ and ACKing the
dead message, you'll eventually end up with the message twice in the DLQ.

The feature only exists because JBossMQ did not have internal DLQ processing.
====

The defaults should be "useDLQ=false" for JBoss Messaging and in its document encourage users to use JBM settings instead.

I created this JIRA as Feature Request because I couldn't reproduce buggy behaviour reported in JBPAPP-3352 against AS 5.1, but I think this change is still desirable for AS, too.