According to the awesome changes in Maniphest and ApplicationEditor I would like to change the global default form.
Otherwise I always get the preexisting one without any changes, when I'm using the following link to create new tasks:
See https://secure.phabricator.com/T9908#147034 and @epriestley answer
Basically core dev are aware that you can access old maniphest by clicking on big + button.
It still a question what form should be displayed and then implement it.