Case in point, Jeff. You're an engaged user, and your vote is "Meh". How "Meh" do you think the non-engaged users are (positively OR negatively?). The vote system's a good start, but it still only engages a fraction of the user base, one that has mostly, for as long as I've lurked on the forums, given 'meh' responses to frequently requested features by more casual users (who tend to only show up when they feel like the product they regularly use, and increasingly fork out for isn't meeting their needs).
It certainly is: to me, more is more. I like to slap a lot of different labels on things, that's the benefits of tags over notebooks, that said, it means I end up tagging two different words with the same meanings, or plural/singular variations on two different notes. Let me search for one and get the other.
Simple: Synonyms are local, they apply to all notebooks you have - if you share a notebook you have to define the associated tags - what the user does on the other end is their business. eg. Bob shares a notebook and has a note with "building" as a tag (the verb, for the purposes of this example), on his end "building" is synonymous with "construction". On your end, you see "building", but you may or may not have "construction" as a synonym - it doesn't matter- but 'building' will inherit the same synonyms that you have for "building". Not if you use 'Building' as a noun, you may get some odd matches - but it's not a hard thing to add an option for whether users inherit synonymous tags or not.