Awesome sets—I use the 2B 10px Pencil brush for quickly sketching tight wireframes in Photoshop. Wish he would release brushes for Illustrator as well.
Hum... I think AI brushes are a bit tricker... and less effective.
I like how his brushes are actual brushes intended for drawing and not clones of greyscaled photo crops like 99% of all free PS brushes are.
Guys, you have to check Kyle's brushes out . They are super awesome, they work as expected and they are super-cheap...
He also have some "free" brushes, but I must warn you, Your are going to love them... Watch the videos!