What Makes Dickey's Knuckler So Good?

A variety of speeds and an ability to throw it for strikes:

After years of work, Dickey mastered the virtually untamable pitch by coming up with two innovations in the way he throws it. First, he pitches it faster than any other successful knuckler has ever done before. Tim Wakefield, the only other knuckleball pitcher in the league when Dickey started learning the pitch, threw it at a typically snail-like speed of 67 miles per hour. Dickey throws it on average at 77 mph, changing speeds with a slow version between 73 and 75 mph and a fast version between 75 and 80 mph. This “angry” knuckleball is like no pitch big league hitters have ever seen before.

Dickey also came up with a clever way for perfecting the mechanics of the pitch. Charlie Hough, a legendary knuckleballer and Dickey’s mentor, initially taught him how to conceptualize the knuckleball throwing motion. He keeps his body compact by imagining that he is projecting himself through an open door frame with each pitch, and that his goal is to avoid touching the sides of the frame. Dickey took this concept one step further and began to visually project the door frame toward the plate, shrinking it to the size of a vertical shoebox. By aiming to throw the ball somewhere inside this imaginary vertical shoebox, he is able to make sure that the unpredictable pitch lands at least somewhere for a strike the vast majority of the time. 

I'd say he's almost a lock for the Cy Young.  Gio Gonzales ended up with one more win than he did, but Dickey had a better ERA and led the league in strikeouts.