I am using Evernote for more than 4 years and after reading Michael Hyatt his excellent blogpost called:
How I organize Evernote, A peek inside My Personal System
Michael Hyatt how I organize Evernote
So, I changed from Notebooks to tags, and it is great......... on my MAC, but searching and using tags on my IOS devices are unfortunately not so.
NO nested tags.
Even Scannabel does not support tags al all.
Boys and girls at Evernote: hurry up!!!!! You are lucky that OneNote (at this moment) has an awful tags system)
greetings from the Netherlands