Until today nobody has been able to verifiy the existence of a trusted platform module (TPM) on the Mac Pro. There has been speculation that this was due to market timing, because Intel's reference board design did not include one. HD-content owners have made clear from the beginning that a protected content path is of absolute necessity for HD playback. A TPM really makes this a lot easier as any involved drivers can be digitally signed against it. Apple has earned a bad track record concerning early adopters in the recent years. Hopefully they don't 'fix' this issue with the Blue Ray enabled Mac Pros locking early adopters out again. (They could argue: "Hey it was supposed to be a work horse, no entertainment platform").