I just got a CO2Art regulator, there are a couple threads out there started by me on them. I think it's a good regulator except the needle valve. It could be that I got a bad one. But it is not consistent at all, and can be too fast or too slow when you turn it on - it somehow drifts from its settings very easily. I ended up getting a Milwaukee pH controller for peace of mind and so now I don't worry about the needle valve being exact, the controller will cut off CO2 if the pH drops too far.
CO2Art customer service was spoken of very highly in the past. That has not been the experience I've gotten. It's been a rather bizarre experience and they have not really gotten back. I received an email from them a week or so ago that where they asked for shipping info and said there might be something wrong with the needle valve I got and they would send another, but I have not heard from them since. There is something strange going on like maybe the company is in some kind of transition.