Yesterday's Legends and Lore article was quite possibly the best news about D&D Next that I've heard in a while. Feedback from the first playtest packet not surprisingly indicated that the Fighter was boring, and that the class needed its own unique mechanic instead of just having higher damage, HP, AC, etc. I personally wasn't terribly concerned because I knew that they had a more tactical package for Fighters in the works, though admittedly I wasn't sure how it would relate to the playtest Fighter (namely, what it would give up in order to avoid being flat-out better).
The answer is Combat Superiority. And boy oh boy is it a good answer. The basic idea is that a Fighter has a number of Combat Superiority dice that he can use on his turn. The most simple, basic application of these dice is to just roll them as extra damage. A more tanky Fighter, on the other hand, might roll them to reduce incoming damage. Some defender options might be to reduce the amount of damage an ally takes, or to use them to add to an ally's AC (or debuff an enemy's attack). Note that the dice don't need to represent a rolled value; for example, I can see this as a nifty way of replicating 4E powers on the fly. The basic model for a 4E power was damage + effect, so 3 different powers might look like this: 3[W] vs 2[W] + prone vs 1[W] + daze, the idea being that you trade out damage dice for effects, with stronger effects costing more dice.
See the potential here? DMs can be advised how "expensive" certain effects and actions are, using the published maneuvers (like the examples from the article) as a baseline, and they would be ready to deal with any improvisation that a Fighter's player might come up with!
Once the Fighter levels and gains 2+ CS dice the amount of potential choices during a turn could easily satisfy a more tactical player*, with the resolution remaining relatively simple. There wouldn't be as much choice paralysis as, for example, choosing from several encounter (or daily!) powers that you won't be able to use anymore this battle. And those who prefer simple "I hit with my sword" Fighters can easily just default to using those CS dice as extra damage.
Mearls and Co. stated that they wanted to have a "dial" built into classes so the level of complexity could be toggled, and on this point they definitely succeeded with the Fighter!
*I'm thinking along the lines of "I use one of my dice for defense, and one for extra damage, vs I'm going all in on damage vs I'm going all in on defense, multiplied by the possibilities that all of the different maneuvers add, and throw in some occasional improvisation for good measure!