The pop up for "just now" etc. on the new timestamps is very inconsistent and doesn't work well in general. Sometimes it works, sometimes it doesn't.
Specifically, I have found that i and fails to pop up entirely when you've just hovered over something else, which a very common occurrence as I hover over people names when going between messages and also if I'm checking and someone sends a message I will lose my place and hover over a name or something.
2. Hover over any message and timestamp bubble won't show