The green brick is a popular hone. Dig through past threads, and you'll find this rock discussed thoroughly.
The green brick is far muddier than any other synthetic I've used. This makes it a suitable choice for maintaining a convex grind.
It dishes quickly, but not so much that I've ever had to flatten mid-job
I use it exclusively to finish stainless knives for friends. For my own knives, I prefer naturals. When I used synthetics, I jumped from 1k to 5k.
I think it is an excellent choice for a practical edge.