As a brush, it is excellent. It takes a great deal of skill to use this instrument as a *pen* however.
It is difficult to tell what stroke width you'll get without a lot of practice, and it will change as you move your hand across the page - again, unless you have a lot of practice.
The curved blade makes it difficult to draw sharp beginnings and endings, as well as giving the strokes their characteristic rough edges. It's more like a round chisel than a square one.
The nib is durable and stiff, made of brass, and its vanes are in proper alignment. The holder is exactly what it looks like - a standard speedball. The whole kit comes in an attractive oval plastic tube.