It's always nice reading from a skeptic that he eventually liked the game, Celtavian. (Not that your critic was entirely invalidated by this - the Wizard is still nerved and less flexible then in 3E)
Now I think, for balance, that some of us "lovers before release" guys stand up and declare that ultimately 4E turns out not be what they want and go back to 3E.

Wormwood, I nominate you.
Okay, a little more serious:
D&D it is because of the name of the cover, wizards stilll cast magic missiles, fighters still kick as in combat, Thief are still backstabbing bastards that defuse traps and open doors, and Clerics still heal people, and because my group declared the experience they had playing it as D&D.
D&D it is not because the seperation in power acquisition between spellcasters and non-spellcasters is gone, because it no longer uses skill points and thus is no longer a "logical" evolution from rogue/thief skills non-weapon-profiency to skill points, and probably still a few other points.
4E seems to have had alot more thought put into the coneptual idea of what an encounter should be like, much more thought than previous editions.
Again, I am not familiar with editions before 3rd, but the whole CR/Encounter Level system of 3E for me was genius - a system that allowed me to gauge how hard an encounter will be for my PCs? I hadn't seen that before, nor I have seen something after. 4E is clearly a refinement of that prinicple. It is probably also an ultimate expression of "gamist" concepts in D&D, only existing to facilitate the "kill people and take their stuff" trope, but, well, I think it is a very powerful and important tool for DMs. Expanding the system to handle "skill challenge" and quests just seems logical.