the main reason i mainly stick to notebooks is because it requires slightly less effort than tagging. like when creating a new note on the desktop version, the notebook will automatically be selected but tagging involves 2 extra steps, clicking "add tag" or "f3", and then typing the name of the tag. when a tag is selected from the left menu and you make a new note, its created in the default notebook but the tag that was being viewed isn't added to the note. it's the same deal on android but slightly more awkward because of the screen size.
it sounds fairly insignificant but even though ive tried tags many times i still end up adding to notebooks because its just that bit quicker and easier. i think if the process of adding tags had a bit more polish i might be able to switch.
like having the tag list pop up on windows instead of having to type first would mean a tag could be using only a mouse. if 3 or so recent tags were listed it would make it quicker and maybe 3 suggestions/predictions, something similar to how the web clipper works. these would make it even easier on the mobile version of evernote.
also when typing tags it just uses a basic search instead of fuzzy. why hasn't that ever been updated? for example if you want to add the tag "SomeName" and can only remember part of the name and type "Name" it wont show up... you have to type "Some" from the very beginning or else it disappears from the list.
there are plenty other little things about tag entry that could be improved that i wont get into but i think its all very strange when people say evernote is best suited to tag use instead of notebooks, yet evernote seems to be designed better to add things to notebooks. so something doesn't add up. even the new android widget lets you quickly add a note to a notebook, but not to a tag.