Not at the place that I support. They use a 6,000 CPU IBM Blade as the server with various high end Unix/Linux workstations that are far above the Mac Pro's specification.
Granted I only support the one place but they are big and the software that they use to render Movies is a Unix Only Piece of software if I remember correctly. It may have been ported to run on BSD/Mac whatever OS but it was originally written for a Unix/Linux depending on the place that it's used. Even the biggest Mac Pro can't hope to compete with that Blade no matter how they are configured. Let alone considering the cost of the thing.
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