Cata's almost here, and I think I have something that'll make questing a bit easier.
DoubleClickForTheWin's main feature is that it'll let you advance through most NPC gossip/quest panels simply by double-clicking anywhere on the frame.
It'll always try to pick the-right-thing, so if the gossip has 1 available quest, one
complete, and one uncomplete, it'll pick the available quest for you first and then hand in the other one next time around. Or select the vendor option from innkeepers, etc.
It won't do anything if there are multiple quest reward options, just so you won't make mistakes when quickly double-clicking away.
And on top of that, it also handles few other cases where you'd have to wave your mouse cursor back and forth all over the screen to accept popups and clicking buttons. Check the project page for full list :)