I've never used it but I know people enjoy it and will be sad to see it go. I hope you can still find ways to connect with any friends you've made there.
I've made a few friends there over the years but they mostly had moved on now (and me too) so I don't really care about it apart from I probably wouldn't get the weekly coins anymore.
I never had the privilege to play on Miiverse. Now that it's ending I feel like I missed out on the fun. I never cared to play it so it doesn't bother me that it's ending tomorrow.
But yeah I don't really care that miiverse is going away, as long as I get my archived posts... I'll never forget my first miiverse post. It was a drawing a grrrol xDDD