I agree with all these posts.
I recently upgraded from Evernote Free to Premium despite all my friends moving to OneNote primarily because I feel Evernote tags are a great way to organize/search and want to support the company.
I learned about nested tags today and think it's an amazing feature. I completely redid my notebook organization and tags based on nested tags only to be disappointed when I loaded my iOS app and found out there's no nested tag support. I now have to go back and redo all my tagging since my new nested tagging organization doesn't work on the mobile app.
Evernote Devs: PLEASE add full nested tag support in the mobile app. This is an excellent feature that makes Evernote stand out against OneNote and all other note apps.
The suggestion of adding boolean tag searching is great as well.
Thanks for listening, hope to see this in a upcoming update soon!