I have one. I don't use it a lot, but I like having it. The biggest issue I have is it can overheat too easily. I was hoping to use it to sear steaks after cooking the sous vide. However, getting the case iron hot enough to do that causes the burner to stop because it's over heated too quickly.
OTOH, for normal cooking and simmering, it's really good. I get a lot of control over the heat and it's quick to heat. So, it's a bit of a mixed bag depending on what you want to do.