UPDATE: The article has finally been errataed in the Dragon magazine compilation. There are details below, but the most important error - the Warding Steel power - is fixed now.
The new Class Acts article devoted to Fighters (how many are there, already?) provides much needed reasons to make a Greatweapon Talent Fighter, by far the most overlooked of this class' builds. There's a lot to comment - to summarize, the article makes a great read, and is mostly safe to use in your campaign, with two notable exceptions I'll explain below.
The new feats presented in the article are something the class has been missing greatly, ever since Martial Power was released: Fighter options that can't also be taken by Battleragers or Tempests. Most of them are decent and moderately interesting, but there's one that really sucks, a very strong one that will be very influential in future fighter builds, and one that is quite broken.
The crappiest new feat is, sadly, called Fighter Weapon Specialization. One would expect such a name to be used for something really cool, but this amounts to a mere +1 to damage with your chosen weapon type, which never increases. What a letdown.
The feat you will have to take into account whenever you make a Fighter PC from now on is Hewing Charge. It's the ultimate reward for going the 2H-weapon talent route, and grants a Con bonus to charge damage. This has the potential to embarrass Howling Strike Barbarians, and asks you to build the character around it. Nevertheless, I think it isn't really unbalanced, considering what you can get from other Fighter builds. I really, really like it.
The broken one is Pinning Challenge which, despite its name, doesn't have nothing to do with Combat Challenges or Opportunity attacks. It allows you to immobilize with basic attacks, and it's wrong at so many levels! Against melee enemies, this allows you to effectively stun them at-will, for the whole encounter. What's worse, nonbasic attack powers become really unappealing once you have this. A real blunder.
A version of Pinning Challenge that is both cool and balanced just requires you to add 'When making a Combat Challenge attack or an opportunity attack'. I strongly recommend you to use it, or something similar, at home.
By the way, the Mastered Technique feat, which is conceptually sound, won't work in practice because it grants a +1 feat bonus to AC, but every Fighter worth his salt won't be able to stack it with the +1 feat bonus granted by Armor Specialization. Since it absolutely needs to be a typed bonus, why not change it to +2?
There is a neat selection of new powers, typicaly centered on 2-handed weapon wielders, but without actually requiring the Weapon Talent class feature. The core mechanic for attack powers seems to be granting -2 to hit for a bonus to damage (usually) Con. At first sight, this is terrible unless the bonus is huge (which it isn't), but some of the powers manage to be decent.
Brutal Advance (Daily 5)
A multiattack power, exclusive to 2-handed weapon wielders. Hit, push, then charge. This should amount to a great deal of damage.
Line in the Sand (Utility 6) (Update: changed to daily power in errata)
An amazing example of justifying Zone powers for martial characters.
Hurricane Strike (Daily 15)
This targets "any enemy in burst". This deviates from the usual "each enemy in burst", but judging from the powers, they mean the same. Weird. Maybe it's supposed to work like previous powers, but allowing you to skip enemies?
Warding Steel (Util 16) - Completely broken as an at-will. A permanent bonus to AC equal to Con, and you can activate more than once per turn (it stacks!). It really should be an encounter power. (Update: Finally changed to Encounter. The world is saved)
Toppling Finish (Daily 19)
This is a promising 2-hit power: the first attack knocks prone, and the second hurts a lot. The problem is, it has the reliable keyword, so you can 'spend' the reliability with a hit that deals no damage, then miss the important attack. Maybe they could add a line like "Hitting this attack doesn't count towards the Reliable keyword"?
Battle Furor (Utility 22)
Permanent Stance! It's an encounter power, so you can have it always up. It's effect is to turn excess healing into temp. HP, and then grant some extra damage. Very cool.
Two, exclusive to Great Weapon fighters. The Great Weapon Master specializes, oddly, in defensive maneuvers and counter attacks - the 16th level feature grants a Con bonus to damage against enemies that have missed you. It looks more fun to play than the average path, and isn't too bad at the power level department.
The Siegebreaker' Shtick is to weaken enemy defenses. It's damage enhancing feature is what the Pit Fighter's should have been all along: ability modifier damage (Con instead of Wis, here), limited to once per round, and only when you have combat advantage. This one also features a permanent (that is, once per encounter) Stance, called Brutal Momentum, which grants bonus to attack after hitting with at-wills.