I believe there are two categories of people: those who work on projects using Evernote, and those who don't.
And the last ones sincerely don't understand why is the feature they don't need is needed for anybody.
in my opinion, http://theguide.sourceforge.net/ had the best hierarchical structure view and the user experience for working on projects.
When you write a note, at some point you might need a deeper structure, so you create a note inside a note, and each of them has a content.
Differences compare to tags:
notes don't change the order based on recency or name, only by user explicit actions. hence a user can leverage visual memory for better navigation
only one parent, so I don't need to remove the old tag, assign the new one, and it's not possible to make a mistake during these actions
I can see all the notes inside a parent in the same view, so again I can use my visual memory to the fullest extent
any parent can have a content, so you can start with the main idea and detail it with child notes
Evernote parent tags contain everything that children and children of children contain, therefore I have to click on all the tags lower on the hierarchy, remember all the notes and compare what I've remembered with what Evernote shows me to finally find out what are the actual children.
Tags are really bad for this purpose. I use a note with structured references instead.
Don't get me wrong, tags are good but not for that.
The better solution for adding this type of view is to make it as a separate database or hidden note with information about references and structure. When you turn it on it's empty, regardless you already have notes. and then you can move notes in that view. So this feature won't affect you if you don't need it, and you can use it selectively.
Differences compared to a note with internal links:
it's always at the navigation panel
you can use drag and drop
a note in single hierarchical view can have only one parent and you can't accidentally duplicate references
it has an ability to create or remove notes right from the view.
I would definitely buy a Premium if Evernote had a good hierarchical structure view.