Looks like Mike Mearls bought and read Dragon Warriors--geez, that was fast; I guess that's why he gets paid the big bucks--and he has this to say:
1. Take the D&D 1983 Red Box.
2. Clear out all the goofy, arbitrary things in the rules and replace them with reasonable alternatives (like explaining what happens when a spellcaster puts on armor).
3. Add a spell point system with several different types of magic.
4. Kill the thief's skill system and instead add general mechanics that let all characters do most of those things.
5. Add a vivid, imaginative setting.
He also throws down this gauntlet at the old school community:
In a way, it resembles something that I really wish the retro gamers would at least attempt: take classic games and apply to them lessons learned through playing them. I had the vivid impression from DW that the authors either played a lot of early 80s D&D, or thought long and hard about its shortcomings, and set out to systematically address the game's issues while preserving the feel of a fast, easy, and digestible game.
That seems to echo a sentiment I've seen 'round the old school blogs, actually.