I have the "B" model. Serial #15. Haven't used it extensively, but it's really nice. The build quality is good with a professional fit and finish on the PS, shockmount, and case.
I will say this....the sound of these mics is very affected by the tube. I put a Telefunken in mine, and enjoy more depth and 3D soundstaging than the stock JJ. These mics sound great stock, but with a tube swap, they are really sweet.
Swapping tubes in my old Rode NTK yielded very subtle to almost non hearable differences, but with the CharterOak, it's giant.
I'm doing some large vocal sessions in early January, so I'll get to log some serious time on the thing and get to know it better.