Today WotC previewed Combat Styles from the upcoming Martial Power 2. And there seems to be a lot of them! Lesser styles are feats that can be taken to modify at-will attacks (those listed for the feat), whereas greater styles affect encounter powers (again, only those listed). Styles only work while wielding a certain weapon, and they're also limited by class. It looks like there will be multiple greater style feats for each lesser style (likely to provide fewer restrictions on encounter power selection).
Overall, I really like this system. It serves to differentiate between weapons more (since the feats are weapon-exclusive), but since there's multiple styles per weapon it also allows you to make a unique character for any given weapon. What I like most about it is that it could provide some inspiration for backstory, as certain combat styles might be common only among a specific race or for a specific region. And despite being an extra "complication" for new players (in that it's an extra mechanic), it serves to guide players along a certain theme. If a newbie reads a description of a specific style and finds it interesting enough to base their character's fighting style off of that, then they conveniently have a list of powers specified in the feat(s) that are compatible. Those players intimidated by the thought of searching through 3 different books (PHB, MP, MP2) every time they level up just to pick the "best" power can rest easy; even sub-optimal powers will be more competitive with the bonus associated with a given combat style feat.
I'm actually pretty surprised that the developers have been able to keep the content for this book fresh and interesting. Of course the biggest variable that remains to be seen are the powers; there's already been some redundancy creeping into the system with just the first iteration of "Power" books, and I'm sure the authors were hard-pressed to come up with so many "new" things for a given class to do. Obviously the powers that are associated with the new builds will be unique (though they may resemble powers from other classes, which is fine by me). My concern is that the amount of redundant powers will be increased, and in that situation there's always one power that's "better" than similar powers, invalidating certain options. The classic example of this is the Barbarian's level 3 encounter powers Hammer Fall (PHB2) and Brutal Slam (PP). Brutal Slam is so much better than Hammer Fall it's sick; both do the same [W] damage, but whereas Hammer Fall knocks the target prone, Brutal Slam pushes it 2 squares, knocks it prone, and deals damage to an enemy adjacent to the target. Essentially, instead of tripping the guy you send him sailing through the air and he crashes into his friend. Brutal Slam has cooler imagery and it's mechanically superior. Hammer Fall, which used to be a decent pick, is not going to be picked anymore by players that have Primal Power. In effect, you've "de-valued" your PHB2 by picking up PP because certain powers become wasted space.
I'm not saying this is a huge problem; obviously with so many different powers to choose from some are bound to be great and some are bound to be sucky. What bugs me is that sometimes sub-par powers can be a viable choice if they adhere to a specific mechanical and/or roleplaying concept, but not if there's a better power that does essentially the same thing. It's probably not a big enough deal to worry about in the first set of Power books; I just hope that it doesn't become more widespread in the sequels.