I've yet to see these notifications appear in the bottom left corner as people have stated/screenshot.
Not sure while, but I'm running Chrome (latest version), but I'm also behind a corporate firewall. No idea if that matters or not.
I assume that I should see that popup for alerts such as "likes" or "replied to thread" that show up at the top of the page?
In fact, as I clicked there to get an example, I just got a "like" on one of my posts, never saw the popup. Maybe I'm just not noticing it. heh