Great lesson, realy boosts your accuracy and speed, not only for scales, but for chords and any movement over the fretboard.
I have noticed one thing while practicing this one, and I hope it will help many of you.
I started to do this exercise in a slightly different way (can't remember why
) and noticed a big improvement.Instead of pressing down on fret, I started to play muted notes.
So, try just to touch strings with your left hand while doing this exercise, and then, after a while, start applying the pressure (play notes regulary).
Hope it helps.
Regards from Serbia,