No, that's deprecated API. Use an IDE that supports phpdoc and it'll tell you what API calls are deprecated as well as typically in their description we put what new API call you need to use. In this case you should be using a use statement to access the UserTable namespace or pathing to the namespace. Examples as follows.
Use:
Code:
use CB\Database\Table\UserTable;
API:
Code:
$user = new UserTable();
Without Use:
Code:
$user = new \CB\Database\Table\UserTable();
Below is a more up to date registerUser usage. We'll update the API tutorials when time permits.
www.joomlapolis.com/forum/153-professional-member-support/228495-solved-cb-version-api-cb-version-205#258806