Limitations

Topic names cannot contain a wild-card character in topic creation. For subscription expression on the template characters ( or (#) with any number of delimiters (.)) can be used. Usage of any other template character throws an exception in 'lookup'.
Deletion of a hierarchical topic that has active publishers/subscribers is disallowed. Care needs to be taken not to delete the hierarchical topics when any topic in the hierarchy contains active publishers or subscribers.
A publisher cannot publish on multiple hierarchical topics concurrently. A publisher has to specify the complete name of the hierarchical topic on which it wants to publish data. Creation of a publisher on a topic that contains an asterisk throws an exception. Similarly, an exception is thrown if a publisher tries to publish on a topic which contains an asterisk .
If a subscriber subscribes on hierarchical topics with a subscription expression, and the ACL of a 'child' in the hierarchy is changed by the administrator mid way through receiving messages, the subscriber remains unaffected by this change. However, creating new subscribers with subscription expressions will get affected by this change.
There is a performance degradation associated with hierarchical topics. Users are advised not to use hierarchical topics for applications where performance is a major requirement.