I have just posted this letter to ZBrush support. Feel free to copy it.
Dear Pixologic, I have just read your announcement regarding the development of ZBrush for the Mac OS X platform. According to the announcement you will not be producing version 3.0 or 3.1 for OS X.
It is my opinion that this is the second time you have broken the agreement between you and myself when I purchased in January, 2008. According to our agreement you would supply me with a Windows capable version of ZBrush 3.1 while you completed the development of the OS X version. It was implied that the OS X version was nearing the end of its development. Since there is no version of ZBrush which runs under OS X on my machine (MacPro) what you were actually selling me was a product I could not use without further purchase of the Windows operating system or until you released version 3.1 for OS X.
What in fact was the case was this: The OS X version had not even been put into beta testing. I know this since the invitation to beta test went out near the end of February. Since the beta was not public, I have no way of knowing what version you actually seeded to your testers, but the implication was that it was 3.1. So there was at that point the tacit promise that you would in the near future be supplying me with the promised software.
It is now five months later. You have effectively cancelled development of the software you promised and indicated that you will not be delivering anything I can use for at least two months. Given your track record, I don’t expect you to make good on this promise either.
Therefore I ask that you refund the full price I paid in January without delay.
If in the future you produce a product which will run under OS X, I will consider purchasing it.
Thank you
Will MacNeil - Animation and Editing