Not all.
The last Tag Meta version add support for placeholders. These are not introduced for the J1.5 version. Joomla 1.5 has reached the end of life and is not supported yet, and the effort to mantain the code updated is not trivial.

You should consider to upgrade your sites to Joomla 2.5 as soon as possible.

Kind regards,
Luigi

Just remember this is not the final 1.4.3 version, cause we are adding new features to this version yet (maybe placeholders too, if many users ask for).

Luigi