Oddly, I just updated to 2.3 b2 and users immediately noticed that user mentions (tagging) isn't working. I see that also on this site.
As you type @User... all the available options pop up but if you select one, nothing happens.
This promotion ended up being cost prohibitive for those of us who renewed under the impression that the release of 2.3 was imminent.
Obviously I wish I had just waited.
What has been appealing to many on my forums is that it's 100% anonymous, and in my particular case, absolutely no ads or tracking of any sort. That appeals to many people but yeah, making a new forum sticky to people who've grown accustomed to social media is a challenge indeed.