I voted for Knight as the superclass name, but I also prefer Champion.
A Cavalier / Paladin / Knight champion of justice sounds awesome. Spend all your character customization options to really get the full she-bang of "Knight in Shining Armor". But in games where horses are few and far between, or you just don't plan on using your horse much, I think Cavalier could be skipped. (though the subclasses should still have a supernatural method of summoning their mounts, it's just that the cavalier specialty would confer additional combat maneuvers / bonuses or skills while ahorse).
I also wanted to say, it appears as though, from Mearls' podcast, that many of the better suggestions from this forum, such as Ws instead of MDDs, have made it into the game. Keep it up! We'll have a workable set of rules soon at this rate, ones that strike a good balance of useability and common sense while avoiding pitfalls in other editions. I read some of the comments on the Wotc site and there are quite a few people there who say that e.g. daggers should do the same damage as a greatsword. Ugh, I'm glad they're not designing this game and their "gear is mere fluff" mentality has not polluted DDN. In fact, I think Enworld's comments and debates about these things has led to a great many improvements that I directly see applied to what they've mentioned in the playtests, if not exactly, then at least addressing our concerns in new and creative ways. E.g. how to make rangers distinct from a fighter + specialty + background.
I have similar hope as a result that they'll adjust the Paladin superclass name to Champion (or Knight would work too, though I think that would be better as a paragon path / prestige class). To be a knight, you first have to be a squire, right? Earn your title, don't start at level 1 with it. Knight sounds more like a veteran paladin or fighter prestige class to me, and not something you could simply chose to be from the start. Prove your valour!!