I don't often miss game mechanics, at least not on a regular basis. Sure, sometimes I whine about not having Divine Intervention anymore, but honestly it's an artifact of paladin past and I've accepted that.
But I just can't get over not having Aura Mastery work with Crusader Aura anymore. I miss it every time I log in.
A lot of times, I use it just to hear the sound it makes, but I get sad, too, because Aura Mastery has two sound components: the shing of AM and the rahw of Crusader Aura. It only makes the shing now.