I'm glad that people like the book, and I'm also glad that people have reacted in a way that we hoped they would. Namely, that warriors need a boost compared to spellcasters.
Back when 3e first came out, the fighter class was really interesting. It got a ton of feats. Something like triple as many feats as anyone else. I clearly remember my first 3e fighter, a Beorn Battlehelm. Beorn was really fun to play up until around level 8. At that point, I figured out that I couldn't find any feats to really improve Beorn's main focus: two weapon fighting with a flail and battleaxe, with some tripping thrown in for good measure.
The problem with making fighters rely on feats is that feats are also available to all the other classes. Furthermore, feats never had a level structure comparable to spells. A "better" feat just had a long list of prereqs, and there were no guidelines on just how good a feat could be. Thus, feats tended to cluster around the same power level.
In walks the fighter. His class features are feats. Since all feats are roughly the same power, and there is little additive effect outside of trip builds, he very quickly plateaus in terms of effectiveness. It would be as if a wizard still had spell slots for levels 1 to 9, but spells were never more powerful than a 3rd level effect.
There have been exceptions, but in general it's hard to make a fighter who's relevant at high levels. IME, most people who manage to pull it off rely on magic item combos and trip-based builds.
Nine Swords reverses this trend by building combat maneuvers that, at high levels, are on a power curve equivalent to (though not the same as) spells.
