Works fine for me, and I suspect most people.
You need to give us information about your platform/OS/CS version, ACR version etc etc before we can help.
Well, it worked fine for me as well for the past couple of years. I had not had any problems using it for the past few years. I use a Mac OS X Yosemite. As far as I can tell nothing had changed. I had not added any new updates, and a week ago the adjustment brush in camera raw simply ceased working. Everything else in camera raw works. However, the adjustment brush is a critical tool. I have checked my permissions, and even repaired my permissions with no results. Of course I have also tried several restarts to no avail.