I am usually cautious about horror stories told by apostates, but in the case at hand, that of Miscavige physically hitting other people, I think there may be elements that point to it being true.
Some of these elements are the fact that there are several high ranking ex-members telling about it and that some of them I consider have an aura of credibility and integrity.
If true, it would be completely at odd with the principles of Scientology itself, that would put emphasis on the power of intention alone. There may be some elements of physical control in the form of reasonable an limited prodding (as in the case of TRs), but nothing like hitting, hurting, restraining, or any other form of actual physical force.
Particularly ominous, of course, would be if that violence was conducted against women, but even just the fact that violence at all would happen would definitely put the CoS in the wrong track, in every sense of the term.
If I was a Scientologist, I would be concerned about this kind of allegations and ask that full light be made on them.
The Associated Press: Report: Violence common among Scientology managers