Well, from the perspective of "the game" (rules, units, etc), there have only been tweaks to the enhanced set. These are due to rare combat situations. The enhanced set is a little different in that supply is now abstracted (no supply unit) and there is no movement capture combat. It is kill only (except for city capture of course).
From the perspective of the interface, a great deal has changed since the KS. Not the whole look, but many more commands have been added, other data is customization has been presented. Yes, I do need to do a stream for this.