Hello Michael,

thanks for your post.
Of course using the latest version with Joomla 3 will give you access to all the latest features.

By the way my advice to exclude users, is using Joomla ACL and access levels.
The chat is based on a system plugin, so it would be enough assign the plugin to a different access level to make the chat appear only to specific users.
Of course Joomla 1.5 still lacks dynamic ACL and by default you have only 3 predefined public/registered/special

Best regards

John