This is not Dungeons & Dragons.
Or at least if Dungeons & Dragons 4th Edition is Dungeons & Dragons, then it is not the Dungeons & Dragons as the gaming hobby has known it for some 34 years. For a mere five years after the last rules update, Wizards of the Coast have given what is the most well-known, number-one RPG the most radical of makeovers. This is, in fact, even more of a radical redesign than the intellectual property received when it was upgraded from Dungeons & Dragons to the First Edition of Advanced Dungeons & Dragons. It is, though, a redesign that is more in keeping with contemporary gaming -- more so than with either Dungeons & Dragons Third Edition or Dungeons & Dragons 3.5. For Dungeons & Dragons 4th Edition is heavily influenced by MMORPGs (Massively Multi-player Online Roleplay Games), such as World of Warcraft, and by the Dungeons & Dragons Miniatures Game.
It is definitely not Dungeons & Dragons in the sense that, although Wizards of the Coast will still call it Dungeons & Dragons, the average gamer will not. With previous versions of the game -- including variants such as Castles & Crusades or Paizo Publishing's Pathfinder RPG -- still offering plenty of viable play, gamers are going to need to identify which version of Dungeons & Dragons they want to play. So to everyone bar its publisher, this is not Dungeons & Dragons, but "4th Edition."
I think that last point is particularly well put. I do not envy the uninitiated newbie trying to get into the hobby on his own in this day and age. It's funny, but I think that your prototypical newbie is better off venturing into a Borders nowadays, since he'd simply be presented with the 4e books rather than the myriad of d20 products he'd find in a FLGS. Is that another sign that the time of the FLGS is passing?