I think it would be useful if the user list in the "What's Going On?" area was sorted by last activity instead of alphabetical. A lot of forums sort it like this, and it's weird that vBulletin doesn't. Makes me think the end of the alphabet users were active longer ago.
There was once a mod that could do it:
https://vborg.vbsupport.ru/showthread.php?t=233369
But it doesn't work with 4.1. Also, that one has a lot of unnecessary stuff like letting the user choose.