The GUI won't allow me to turn it off without powering down the VM first. I found a little powershell code which seems to do it live but it's just one more thing to remember to do.
I want it disabled because I've seen a bug or two in the past and it's something I don't want to worry about. In fact, there's a new bug in ESXi 6 with CBT: http://kb.vmware.com/selfservice/micros ... Id=2114076
Since VeeamZIP always does a full backup anyway, having it turn on CBT doesn't help and in certain cases might cause problems down the road.
Long story short, I want to keep things as simple as possible and taken an occasional backup or a vm or two. Turning on CBT, for zero gain in my situation, just adds one more thing to potentially cause problems.