If you were one of those people, like me, that would have application control sessions blocked after a failover on HA then 5.4 may be beneficial for you! See below!

VOIP application control sessions are no longer blocked after an HA failover (273544)

After an HA failover, VoIP sessions that are being scanned by application control will now continue with only a minor interruption, if any. To support this feature, IPS UDP expectation tables are now synchronized between cluster units