#1
I'd like it if there were some kind of notifications for people responding to you in-thread.

Like, if someone quotes you, or maybe puts "@[username]" or some similar "code".

Some times you ask a question or something and keep F5ing the thread or even going as far as searching your own username (to see if someone responded to you) and that's either a little time-consuming....or maybe a little creepy >_>

If not notifications (I think emails-PMs would be too much and maybe too much of a hassle) have a separate tab, for instance next to the "Control Panel" or "FAQ" ones that keeps track of all responses so you just go there and check it out.
#2
This has been suggested many times before, the reason it hasn't been implemented already is because it can't be implemented on this version of vBulletin.
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#4
Anyways you guys use vBulletin 3 then?
Does it have a license that doesn't allow you to change its source code or is it open source like phpBB for instance?

I don't think it's something that can be that "hard" to implement by yourself by modifying the original vBulletin files/scripts/etc.

The "have a tab with the 'responses' " is even easier I think since that "response tab" is basically the result of a search for your username inside quote tags or in a "@name" tag (although that may need some slight changes).