I've read the Chang book, and so I don't need to refer to the link.
Chang is against Hanon for several reasons: 1) He does not see any validity in Hanon's claim that you can become a "virtuoso pianist" with the 60 exercises. 2) The exercises are all hands together, and there's no provision for HS practise. As a result, Chang feels that the stronger hand does not improve because it is limited by the weaker hand. 3) There is nothing built into the exercises that rests the fatigued hand - as HS exercises might have. 4) Because the exercises are repetitive and easy to memorize, they can easily lead to unmusical, mindless, and robot-like playing.
I believe he makes several other points as well.
With the exeption of #1 above, the other points can be refuted because good teachers who use Hanon tend to use the exercises creatively. In other words, they have students play hands seperate, in rhythms, transpose to all keys (which Hanon advises), use different articulations - which requires concentration and removes the mindless element.
Point #1 is hard to argue against, but short of virtuoso technique, you can certainly acquire some technical advantage through studying Hanon.
I happen to be on the fence regarding Hanon. I think it is misused a lot by bad teachers. If you learn and practice Hanon you may improve your technique to a greater or lesser extent, but no one has proved that you can't do accomplish similar learning actual music.
Chang raises some interesting points about Hanon - and other - exercises. I think he is too didactic in his opposition to them though.
At the end of the day, is Chang your teacher, or are you paying someone else who actually hears and sees you play, and can provide you with advice based on first hand knowledge of you?