You are right. I know for sure that Apple are losing professional audio users. Composers mainly I believe, but possibly also ProTools users. Because many people are questioning Apple's commitment to pro computers because of the nMP... Many people are jumping from Mac/Logic to PC/Cubase these days.—Simon R.
Is it a giant mistake for Apple to not understand it is alienating its most core group of users?
Perhaps most importantly though, is the fact that Windows Vista's newly-implemented security limitations are artificial at best, easy to code around, and only there to give the impression of security. Any program that UAC blocks from starting up "for good security reasons" can be coded to work around these limitations with (relative) ease. The "architectural redesign" of Vista's security framework isn't so much a rebuilt system as much as it is a makeover, intended to give the false impression of a more secure OS.
I have a theory that it's impossible to prove anything, but I can't prove it.