Jayouzts said:
I think the "good" vs "bad" analysis for these misses the boat. If you find the changes good, why not incorporate them into your 3E game now?
Short answer: not everyone is as good a game designer as Mike Mearls.
Longer answer: As I see it, 4e is a working out of the implications for the game of certain changes made in the transition from 2nd ed to 3E, which implications were not fully appreciated at the time of the transition.
A lot of those changes (though by no means all) involved changing the fundamental dynamics of D&D play, from a system with fairly simple character-build rules and almost minimalist aciton-resolution rules which consequently gave the GM a tremendous degree of power in all aspects of play, to a system with complex characer-build and action-resolution rules which shifted power from the GM firmly onto the players.
One implication of these change at the character-build end: 3E makes it possible to build radically underpowered or overpowered characters if a player has a poor knowledge of the relevant game elements (feats, spells, PrCs, etc). As a result, new players can build themselves into a very poor play experience. 4e will try and rectify this to some extent (eg by explicitly calling out character roles, by balancing feats, etc).
One implication of these changes at the action-resolution end: By giving players so many choices, 3E makes combat take a long time to play at the table, and therefore makes it suck a great deal if one's PC is not able to participate meaningfully in a combat. 4e will try and rectify this to some extent, by making meaningful participation in combat possible for all characters all the time (eg by changing sneak attack, by changing the power suites of all classes, etc).
One implication of these changes for the GM: Apparently without really thinking about it (perhaps just following "common sense") 3E extends the character-build and action-resolution rules for PCs to monsters and NPCs. The result is big issues with prep time and play of GM characters. 4e will try and rectify this (with new monster build rules, not giving monsters feats and spells which require the GM to have intimate familiarity with the PC build elements, etc).
These aspects of 4e are all natural consequences of clever game designers reflecting on the implications for play of some key differences between 3E and earlier editions of D&D. They are not changes that are trivial to incorporate into 3E via house rules. And from the game design point of view, they seem to justify a new edition as well as anything would.