Greg Calbi uses Ozone, according to iZotope. So does
Skrillex and
Joey Sturgis, for whatever that's worth. I'm sure more mastering engineers use it than admit to it.
I suspect your real question is: is Ozone good enough for commercial mastering? The answer is "Yes". However, software isn't going to be the deciding factor, as it's far less crucial than the ME's experience and monitoring environment. Mastering facilities spend more on acoustic treatment and speakers than you did on your house.
Of course, that's sidestepping the issue of whether digital mastering is equal to analog mastering. I happen to think it is, but it's open to debate.