The point of the new template system was not to create an editor but to have a new and flexible override system and to allow better names of override templates (folder.tpl for instance). The editor was added to allow simplistic editing, for instance to make a copy of the original template and then remove some elements.
Besides the template editor is useful for allowing people who do not have login access to the server to edit the templates. for instance to do some final adjustments.
Don't get me wrong, it would be of much use to me if the editor actually worked. On my machine, it won't even copy, much less edit templates. If I click on new, assign a name to the template and either copy or start from scratch I get back to the page listing the current templates but not my new one.
