I mentioned before that I started playing D&D a long time ago-- 1977. I think it's one of the greatest game creation since Monopoly. Recently Hasbro/Wizards of the Coast has updated the game. Unfortunately, the purpose of this new edition is not to improve the game. It is to gain control of their property through proprietorizing it.
When the d20 system was created based on D&D 3E, it opened up the game and the rpg hobby in a way that nothing else had. Dozens of publishers began making accessories and adventures for D&D. This was great for the players. However when Hasbro took over Wizards of the Coast, they had to look at this situation and feel like IBM looking at the PC explosion. "Hey, this was our product and now everyone is making one."
D&D 4 gets rid of this problem by doing two things. 1) Bring D&D in all its aspects under the direct control of Hasbro. 2) Create a well-defined look and feel to the game that can't be duplicated by anyone else, by law.