'New Posts While Replying' Notification
 

I use SMF for my temp board (until I can afford another vbulletin license) for when my board is down for maintenance or server issues and I noticed a pretty cool feature in it. And I did a search here and couldn't find a mention of it. Anyways there's a feature that when you reply to a thread, if there are posts made while you're replying, when you hit submit/post it gives you a message saying there are new posts made in the thread and asks if you'd like to view them before you reply. I don't know how hard it'd be to do, I haven't looked into it yet but I think it'd be a nice feature to have on a vbulletin board.

That would be a cool feature, though on a board with 500+ active members it would become annoying :P