In my opinion I will always love the Cavalier class, it is sadly missed in almost every adventure, as well as no longer being a Charcater Class. Why not have an adventure with an NPC that is a Cavalier? Despite it all I'm glad they are at least a Prestiege class. So I can play a Fighter and have all the fun I want with bonus feats.
The Paladin Cavalier oh yes, the ultimate shining knight, but fallen from grace? Why he would be a black knight. hmm the campaign possibilities.