Regarding "Mac exclusively" in professional studios:
Mac computers are seriously lagging behind the curve of hardware development.
Composers who are pushing the limits of hardware (usually composing for TV/Film/Video Games) are literally forced to use custom PCs... because they can't get the hardware they need from Apple.
Was talking with Fred Coury about this during our last conversation.
Many of the top LA composers (Fred, Danny Lux, etc) get together once a month to discuss their craft/tools/etc.
Of this group, even the most die-hard Mac users are running custom PCs as VE-Pro "Slave" machines.
We're finishing up a VE Pro Slave (as we speak) for Trevor Howard.
Trevor is a Mac guy... but needs more power/flexibility.
Mac machines are sleek/slick... but (ironically) not particularly well suited for the "power-user".