This in particular I would argue with. Exept for carrying capacity (which I feel has never had an elegent rule) it is the only place in the system where a stat score rather than modifier count for an effect. Therefore I feel an ineligent solution.4e - set hit points per level rather than rolling
Everyone has the same XP table, regardless of class or race. Finally.
From OD&D:
4 Classes instead of 1
I would go so far as to say 4e's familiar system even rocks out 3e's version. It's elegant, simple, and even answers the "pop-in" "pop-out" of players forgetting their familiars, too!
Which book are familiars described in?
What edition of D&D has only one class?
Also, OD&D has only three classes by default, not four (Fighting Man, Magic-User, and Cleric).
I was suggesting a game supporting multiple roles rather than one was elegant and ground breaking even while being the first hobby RPG on the scene. Most RPGs only support one role like "mythos investigator", "spy", or "superhero".
As I read further and further down the list I started to think "Man! What weird-o alternate reality version of OD&D does this guy have his hands on?!?" 
(Dungeons & Dragons)
Rulebook featuring "high magic" options, including a host of new spells.